Studies in the genus Machairopliyllum ( Mesembryanthemaceae ) , with notes on some related genera

Machairvph\llum Schwantes is a small genus of the family Mesembry anthemaceae. confined to the southern part of central South Africa from the Little Karoo at Barrydale in the west to the Zuurberg near Kirkwood in the east. Machairo­ phyllum is unusual in the Mesembryanthemaceae-Ruschioideae in that fynbos and renosterveld are the preferred habitats. The morphology, anatomy as well as the pollen, seed and leaf epidermis ultrastructure of the genus were examined. The taxonomy of Machairophyllum is rev ised on the basis of data presented. Of the ten names originally described, only four are upheld. M. alhidum (L.) Schwantes, M. stayneri L.Bolus. M. bijliae (N.E.Br.) L.Bolus and M. brevifolium L.Bolus. All four species are very similar in their vegetative habit, and differ mainly in inflorescence and flower characters. Several presumably related genera. Bijlia N.E.Br.. Carruanthus (Schwantes) Schwantes and Cerochlamys N.E.Br.. are briefly dis­


INTRODUCTION
Machairophyllum Schwantes is one of the few genera of the succulent plant family Mesembryanthemaceae which is almost exclusively found in fynbos or renoster veld.The species mostly prefer rocky habitats (Figure 1A, B), although occasionally they grow among grass and shrubs (Figure 1C).In its distribution Machairo phyllum is, with two possible exceptions, entirely con fined to Western and Eastern Cape.South Africa (Figure 2).Two localities have been reported in Northern Cape, but are doubtful and need to be verified (see chapter on phytogeography).
Plants of the genus Machairophyllum are unmistak able, with their clump-forming habit and the smooth trigonous leaves.The leaves have a sabre-like appear ance, which is the origin of their botanical name ( 'Machaira\ Greek, means sabre, and 'phyllon' means leaf).Plants are seldom found in flower as flowering is stimulated by fire.Furthermore, flowers are mostly ves pertine or nocturnal.The striking, fairly large flowers (Figure ID.E) are yellow and frequently orange-red on the outside and on the petal tips.
Ten species have been described of which only four are recognized in the present study.Machairophyllum alhidum (L.) Schwantes.M. bijliae (N.E.Br.)L.Bolus.M. brevifolium L.Bolus and M. stayneri L.Bolus.M. alhi dum is known from several sites in the Little Karoo and is easily recognized by the branched inflorescences and the normally long basal sheaths of the primary bracteoles ('bracts').M. stayneri also has branched inflorescences, and is known only from the type collection made on the Zuurberg.M. bijliae is the most common and widespread species.Vegetatively it looks identical to M. alhidum.but once flowers appear, the difference is obvious since the inflorescences are always unbranched and have mostly short, basal, bracteole sheaths.M. brevifolium.as its name suggests, has short and rather wide leaves.It is known only from the red conglomerate hills between Oudtshoom and De Rust.
Machairophyllum albidum and M. bijliae are fairly abundant.In some cases the populations that were visit ed by the first author comprised hundreds of individuals.It has been suggested to rate M. vanbredai L.Bolus as 'Critically Endangered' (Kurzweil & Linder-Smith 2001), but we now consider this taxon synonymous with the widespread M. bijliae.M. stayneri is only known from the type collection, and the fact that the species was never recollected may indicate that it is indeed very rare or extinct.Populations of the two dwarf species from the crumbling silcrete hills around De Rust (M.brevifolium and the synonymous M. latifolium) appear to be declin ing in numbers due to the erosion of their habitat (Smith etal. 1998: 220).
Machairophyllum is not very popular among succu lent growers because of the often large plant size and the sporadic flowering.Plants are therefore rather uncom mon in cultivation although well-grown specimens may be remarkably showy.M. albidum was introduced into Europe in 1715.but is rather scarce now (Hammer 1991).The plants can endure fairly low temperatures, and due to their fynbos habitat they can tolerate considerably more watering than many other mesembs (Kurzweil pers. obs.).Propagation can take place through seeds or cuttings (Jacobsen 1977).M. brevifolium is not uncom mon in collections in California and England, probably because seeds were sent overseas by Mrs Van der Bijl. a well known South African succulent collector (Hammer 1991: 77).
The objective of this study is to examine the character distribution in Machairophyllum with the aim to resolve the taxonomy of the genus.For the purpose of phyloge netic interpretation, the presumed relatives in Hartmann's (1991) Bergeranthus group, i.e. the minor genera Bijlia N.E.Br., Carruanthus (Schwantes) Schwantes and Cerochlamys N.E.Br., which all share smooth and dotless leaves with Machairophyllum, were briefly surveyed.Out of these, Bijlia and Carruanthus were found to form a very close-knit group with Machairophyllum, which is here referred to as the Machairophyllum complex'.

Taxonomic position and history
On account of having an inferior ovary with parietal placentation and lophomorphic (crest-shaped) nectaries, Machairophyllum is placed in Mesembryanthemaceae-Ruschioideae (Herre 1971).The Ruschioideae is the larger of the two subfamilies of Mesembryanthemaceae with 107 genera mainly in southern Africa.Ruschioideae was classified into 12 tentative groups according to the then state of knowledge (Hartmann 1991(Hartmann , 1993(Hartmann , 1998a)).Machairophyllum was listed in the Bergeranthus group which comprises perennial plants that mostly have free leaves with homocellular xeromorphic epidermis, exserted inflorescences and flowers with separate lophomor phic nectaries.Distinguishing characters of the capsules are the complete, firm and straight covering membranes and the reduced valve wings.Closing bodies can be pre sent or absent.The genera included in this group are Bergeranthus Schwantes, Bijlia, Carruanthus, Cerochlamys, Hereroa (Schwantes) Dinter & Schwantes, Rhomhophyllum (Schwantes) Schwantes and Machairophyllum.Many members of the group also have semi-terete or trigonous linear to lanceolate leaves.The genera includ ed in the Bergeranthus group share a similar distribution in the southern and eastern parts of central South Africa.Hereroa, however, has a wider distribution ranging into The genus Machairophyllum was described by Gustav Schwantes in May 1927, based on M. albidum and M. cookii (here also included in the concept of M. albidum) which he had previously incorporated into the genus Carruanthus.The species were said to differ from Carruanthus mainly by having many stigmas.Schwantes selected the former as the type species.Four years later M. stenopetalum was described by Louisa Bolus (1931), followed by M. acuminatum and M. baxteri in 1935 (all three are here included in M. bijliae).M. brevifolium and M. latifolium (here regarded as synonymous) were described by L. Bolus in 1938.In the same year L. Bolus also transferred Perissolobus bijlii to Machairophyllum.The last two additions to the genus Machairophyllum were M. stayneri (Bolus 1960) and M. vanbredai (Bolus 1964) (here included in M. bijliae).
In 1960 L. Bolus published a brief review of Ma chairophyllum together with a key to the species; M. bijliae was not included as it was insufficiently known.Later this key was used by Jacobsen (1977) in Lexicon o f succulent plants.In her review, Bolus (1960: 156) point ed out that most species were known only from their type collections, and that 'it is quite possible that, when more intensive collecting and study have been done, M. bijliae (in spite of the much smaller size of the type, perhaps due to adverse conditions), M. stenopetalum.M. acuminatum and M. baxteri may prove to be forms of one variable species'.This statement is very much in agreement with the results of the present study.It is interesting that Bolus doubts the validity of her own species (except for the species that M. bijlii is based on, all were described by herself).However, this did not prevent her from describ ing another species a few years later, namely M. van bredai in 1964, which is also merely a form of this 'vari able species' (M.bijliae).The species that Machairophyllum bijliae is based on was first described in a monotypic genus Perissolobus (Brown 1931).According to Brown, the main reasons for the recognition of Perissolobus were its eight sepals; affinities to Machairophyllum were not mentioned in his paper.Bolus (1938) pointed out the striking similarity of the two genera and transferred Perissolobus bijlii to Machairophyllum.She regarded the eight sepals of the species as being 'but a further variation of the already variable calyx of Machairophyllum' (Bolus 1938: 135).Bolus (1950: 229) pointed out that the reason for there not being any reference to Machairophyllum in Brown's paper was probably the fact that at the time Machairo phyllum was erroneously thought to occur in Namaqualand in Northern Cape, whereas Perissolobus bijlii was described from Eastern Cape.
A synopsis of Machairophyllum was presented by Hartmann (2001).Both species with five or six sepals and ± double the number of locules were considered conspecific, namely M. albidum and M. cookii.Also M. bijli ae and M. vanbredai on the one hand as well as M. bre vifolium and M. latifolium on the other hand were united as they were considered to differ only in minor charac ters.Thus the number of species was reduced to seven.It was also pointed out that a study of the genus may show that only four or five species are distinguishable, namely M. albidum, M. bijliae, M. brevifolium.M. stayneri and, possibly, a new species, allegedly from the Richtersveld.

MATERIAL AND METHODS
Dry and liquid-preserved material of Machairo phyllumt, as well as live seeds, were collected in the field in South Africa.For comparative purposes, material of Bijlia, Carruanthus and Cerochlamys was also collected.Herbarium material on loan from the Bolus Herbarium of the University of Cape Town (BOL) and the Herbarium.Royal Botanic Gardens Kew.London (K) was examined.Additional material was obtained from the Compton Herbarium of the National Botanical Institute.Cape Town (NBG) and from living plants cultivated in the National Botanical Garden.Kirstenbosch.Herbarium, live and liquid-preserved material was used for gross-morphological investigations.The scan ning electron microscope (SEM) technique had to be employed for the study of fine details.With this tech nique the examination of seeds, pollen and epidermal surfaces was done without previous treatment of sam ples.SEM investigations of floral structures as well as anatomical studies required the previous fixation of the material in FAA (ethanol 70% : glacial acetic acid : for maldehyde = 1 8 :1 :1 ).Material was treated with FAA for a few days and later stored in ethanol 70%.For SEM studies it was dissected in ethanol.Subsequently, sam ples were chemically dehydrated in formaldehydedimethylacetal and critical-point-dried directly from this reagent without the use of an intermedium, using CO: as the carrier gas (technique after Gerstberger & Leins 1978).Samples were sputter-coated with AuPd and viewed and photographed with a CAMBRIDGE STEREOSCAN S200 scanning electron microscope at voltages ranging from 10 to 30 kV.Anatomical studies were undertaken using a standard dehydration and wax embedding tech nique; samples were stained with alcian blue and safranin.

Growth forms
Machairophyllum species are vegetatively fairly uni form.The plants are compact, glabrous succulents with short stem internodes and trigonous leaves (Figure 1A-C).Old plants may form mats of up to 1.2 m in diameter.Even in large clumps the side branches nor mally do not form adventitious roots and are thus not anchored to the ground.Superficially, plants of Machairophyllum may be mistaken for Carpobrotus, which also occurs in fynbos, although these have some what longer and greener leaves and have well-developed stem intemodes; however, the flowers and the fruit struc ture of Carpobrotus are very different.

Morphology
The leaves are opposite with members of a pair ± equal and basally connate to form a sheath 10-15 mm long; in early ontogenetic stages leaves of a pair are often weakly unequal (anisophylly).The lamina is linear to lanceolate, entire, trigonous in the central portion but basally semi-terete because the dorsal (abaxial) keel dis appears; the apex is acute to acuminate.Leaves are pale green often with a whitish tinge, or frequently flushed with red in sun-exposed specimens.Old leaves die off and turn black, but persist on the plant for a long time.Near the base, just above the union of a pair, an obscure swelling is visible on the upper side, which stretches as a curved structure over the entire width of the leaf.It marks the point up to which the leaf is tightly adpressed to the following leaf pair.However, this swelling is not developed as a prominent pustule, which is found in many other mesembs (Hartmann 1991).
Plants growing wild have leaves 10-± 145 x 8-26 mm.The variation in length and width is continuous and does not allow a clear-cut separation of taxa (Figure 3).Whereas M. brevifolium always has short leaves, a few specimens referable to M. bijliae also have very short leaves, namely Van der Bijl 93 (the type), Desmet 2I5H, Pocock NBG627/26 and Kurzweil 1919.Particularly long leaves are found in M. albidum.It appears that leaf length and width are mainly the result of environmental factors and are not genetically fixed.The leaf size was previously considered a major key character (Bolus 1960).

Leaf surface
The leaf surface belongs to the 'xeromorphic type' defined by equal or nearly equal epidermis cells, a strongly thickened outer cell wall and a prominent wax cover (Ihlenfeldt & Hartmann 1982) (Figure 4); epider mis cells are irregularly polygonal-isodiametric to elon- Leaves lack teeth, dots or hairs, are covered by a con tinuous wax layer, which is either smooth or breaks up into platelets (Figure 4A-F).Local wax projections mainly take the shape of elongate rodlets (Figure 4B-D), but round granules or flakes are also found occasionally (Figure 4B).In Kurzweil 1914 structures resembling burst bubbles were observed next to a stoma (Figure 4F), but nothing can be said about their nature at this stage.

Anatomy
Leaves are mostly well differentiated into peripheral assimilation tissue and central water storage tissue (Figure 5A), which are parenchymatic and have intercel lular spaces.Tannin idioblasts, a common feature in xeromorphic Mesembryanthemaceae (Hartmann 1991), as well as raphide idioblasts occur throughout the mesophyll, but are absent in the epidermis and hypodermis.
Epidermis is homocellular, cells with flat outer periclinal walls without papillae; cuticle 1 to 2 |nm thick; outer wall is strongly thickened at 5-25 \xm and contains crystal sand made up of minute grains of calcium oxalate as in other xeromorphic Mesembryanthemaceae (Ihlenfeldt & Hartmann 1982; asterisk in Figure 6A); inner periclinal walls and the anticlinal walls are 1-3 \im thick; hypodermis cells are elongate or more rarely isodiametric, walls 1-3 |im thick.
Assimilation tissue is compact.10-15-seriate (Figure 6B); vascular bundles as well as fibre bundles are absent; a ring of small vascular bundles is present at the bound ary of assimilation tissue and water storage tissue, referred to as secondary bundles (Dannemann 1883; arrowhead in Figure 6C).The central water storage tissue is 10-30-seriate, contains laxly arranged cells; large water storage cells are scattered throughout.Primary bundles: 1-3, are large with several smaller collateral vascular bundles (Figure 6D); the main bundle is nor mally broad, straight or slightly curved.Most of the pri- mary bundles have collenchymatic caps, and bundles plus their caps are surrounded by parenchymatic sheaths.

Stem
The anatomy of the stem conforms essentially to that of other Mesembryanthemaceae with similar compact growth (Hartmann 1976(Hartmann , 1977;;Hartmann & Golling 1993).
Epidermis and cortex are only visible as separate structures in the primary stem (Figure 5B, D).The epi dermis is similar to that of the leaf, and the hypodermis is insignificant.The massive parenchymatic cortex proba bly acts as a storage organ.In older stems the cortex is successively replaced by a layered cork which originates in its inner part.In several specimens a layer of small and compactly arranged collenchymatic cells is found just outside the vascular cylinder (Figure 5B, C), reminiscent of a similar collenchymatic ring in Odontophorus (Hartmann 1976) and Fenestraria (Hartmann 1982).The vascular tissue of the primary stem consists of a ring of collateral bundles, and takes the shape of a rounded rec tangle with its long axis parallel to the axis of the first leaf.Leaf traces emerge in rapid succession from the shorter sides of the rectangle.Each pair emerges at an angle of 90° to the previous one, and the shape of the vas cular cylinder therefore changes according to this pattern.
Secondary growth starts in the second intemode.It is anomalous as in other Mesembryanthemaceae (Metcalfe & Chalk 1950) in that numerous secondary bundles are developed by new cambium formed on the outside of the primary vascular cylinder (epifascicular cambium).These eventually form several concentric rings around the primary vascular cylinder (Figure 7A, B).An unusu al cell pattern was observed in the pith of several speci mens 7C), looking like pith cells with minute rounded 'cells' between them.It is possible that the latter are in fact intercellular spaces.

Root
Roots are mostly thin and slender, up to 2 mm in diameter.Anatomically the roots resemble stems.They also show an anomalous secondary growth (Metcalfe & Chalk 1950).Roots are usually diarch (2-stranded) or triarch (3-stranded).Prominent collenchyma caps are found on the phloem of the bundles.In some specimens, strongly thickened sclereid cells are found below the xylem and form pronounced sclerenchyma caps.

Inflorescence and pedicel
In principle the inflorescence of Machairophyllum is a dichasium (Figure 8A) which is typical of Mesem bryanthemaceae (Hartmann 1993).The number of flowers ranges from three to ± seven.Frequently one of the side branches is aborted, which is probably the result of envi ronmental factors, or may be caused by disease, or insect attack.In a large number of specimens the flowering shoot is consistently unbranched and has a single flower (Figure 8B), and lateral buds or vestiges thereof were not found.This is obviously the result of a reduction which is also found in some other mesembs and may be part of their life strategy, aimed at a synchronization of the flowering in character of major taxonomic importance, with the order to improve the probability of successful pollination branched inflorescence characterizing M. albidum and M. (Ihlenfeldt 1989: 80).It was found that the degree of stayneri, and the unbranched inflorescence characterizing branching is remarkably constant in Machairophyllum.In M. bijliae and M. brevifolium.This corresponds exactly the present study the inflorescence type is considered a with the concepts of Bolus (1960: 157)  comm.).In the vast majority of cases the distinction of specimens with branched versus unbranched inflorescences is clear-cut but, rarely, poorly grown specimens of M. albidum were found to be single-flowered (however, they normally reveal their affinity to M. albidum in floral char acters).
In all cases the flowers are subtended by an opposite pair of short bracteoles which resemble foliage leaves [These bracteoles have also been referred to as 'bracts', and it needs to be noted that their homology is disputed.However, the term 'bracteoles' was used in the most recent treatment of the genus (Hartmann 2001), and is therefore adopted here], Bracteoles are 7-130 mm long, with their free upper portion ranging from 6-60 mm; bases are con nate and form a sheath.The length of this sheath is strong ly intercorrelated with the degree of inflorescence branch ing: M. bijliae and M. brevifolium.the two species with unbranched inflorescences, have predominantly basal bracteole sheaths of up to 25 mm long (total range 5-12 mm) whereas M. albidum, with branched inflorescences, has predominantly primary bracteole sheaths which are longer than 21 mm (ranging from 15 to almost 100 mm) (Figure 9).The single specimen of M. staxneri (branched inflorescence) has primary bracteole sheaths of 15 mm.The term 'primary' is here used for the terminal flower of the dichasium, i.e. here applying to the basal-most bracteoles.M. albidum and M. staxneri have 'secondary bracteoles below the flowers of the side branches.
Flowers are generally stalked in Machairophyllum.The pedicel is up to 85 mm long in solitary flowers and in terminal flowers of branched inflorescences, is usual ly shorter on side branches, sometimes elongate in the fruit stage, 3-6 mm thick and are smooth on the outside or have pronounced ribs.Anatomically they are rather uniform, consisting of an epidermis with a crystal sand layer, a weakly-defined hypodermis, a massive cortex followed by the vascular cylinder and a parenchymatic pith (Figure 10A, B).The vascular cylinder is a closed ring with inner xylem elements, multi-layered cambium and an outer phloem.All specimens examined have a closed collenchymatic ring on the outside of the phloem.Fibre bundles in the cortex occur occasionally.

Flower
Flowers are actinomorphic and bisexual, up to 65 mm in diameter, with few sepals, numerous petals and sta mens, and up to 12 stigmas; filamentous staminodes are absent.In M. albidum and M. bijliae the number of sepa ls and locules is subject to slight variation (see also Bolus 1950: 229), and different numbers may even be found in different flowers on the same plant.In contrast, in M. brevifolium the number is constantly six.Pollination studies were not carried out, but from a functional-mor phological point of view the flowers can be referred to the 4Phalaenophilous' type (Hartmann 1991: 91).A moth-pollination syndrome is suggested by the yellow flowers with a pale centre which are open in the after noon, evening or at night.Sepals five to eight, unequal, (Figure 11 A) succulent and weakly keeled, with white, membranous margins, apically acute, acuminate or rarely somewhat obtuse, fre quently with subapical mucro on the dorsal side; total length ± 3-22 mm.Sepals of M. albidum tend to be wider than those of the other species, but a comparative analysis of the sizes does not allow a grouping within the genus (Figure 11B).Petals develop as staminodes from the androecial primordium as in other Mesembryanthemaceae-Ruschioideae (Hartmann 1993); are arranged in three to seven series; are ligulate or linear-lanceolate with acute or more often obtuse apex; up to 35 x ± 0.3-2 mm; are yel low or golden yellow and often have reddish, coppercoloured or orange-coloured outsides and tips and paler bases; petal sizes as well as the ratio of the lengths of petals and sepals are largely continuous (Figure 11C, D).
Stamens remain erect during anthesis and form a cone; their bases are epapillate or only the inner ones are obscure Nectaries are meronectaries of the lophomorphic type (Rappa 1912;Hartmann 1991), green.They appear as five to twelve ± prominently raised portions of a ring at the inner base of the stamens opposed to the locules (Figure 12A-C).The number of nectaries is normally identical with the number of carpels/locules.Numerous modified stomata can be seen and are frequently partly blocked (Figure 12F).Crystals were occasionally also observed on these nectaries, both in transections and SEM micrographs (Figure 12E).Their chemical nature is not known, but they are probably not simply made up of solidified nectar, as it is difficult to imagine that crystal lized nectar would not have dissolved during the chemi cal preparation for SEM or wax embedding.In a few specimens there are also structures that resemble minute craters surrounded by a pronounced circular ridge (Figure 12D).In the past, the nectaries of Machairophyllum have been misinterpreted, as they have been termed distant, approximate or contiguous (Herre 1971) which is proba bly mainly the result of their different extent of formation.
The syncarpous ovary is epigynous and is made up of five to twelve carpels which terminate in slender, free stig mas that nearly reach the height of the stamens.Each ovary chamber contains many ovules on parietal placentae.M. albidum has predominantly ten to twelve stigmas, whereas most specimens of M. bijliae and the type of M. staxneri have six to eight stigmas (erroneously 7 or 8 were cited in the description of the species).The two specimens of M. brevifolium examined here exhibit six stigmas (Figure 13).Unlike many other Mesembryanthemaceae, the flow ers of Machairophyllum are afternoon-active, vespertine or nocturnal and remain closed during the day.

Fruit
Obconic, 7-15 mm in diameter when closed, loculicidal, hygrochastic capsules as in most other Mesembryanthemaceae-Ruschioideae (Hartmann 1991(Hartmann , 1993)); their base is funnel-shaped and the top strongly raised in the centre; sutures are prominent and the high valve rims are normally reflexed (Figure 14A).Fully expanded cap sules usually have the valves at right angles to the floral axis.The capsules do not clearly fall into any of the mor phological fruit types distinguished by Hartmann (1988;349) and the genus was therefore listed as a 'genus of uncertain position'.Chesselet et al. (2000) referred to the capsule as 'similar to that of Cylindrvphyllum and therefore perhaps close to the Leipoldtia type", but with spongy tis sue in the covering membranes and small closing bodies.
Within the genus Machairophyllum the internal struc ture of the capsule is not uniform (Figure 14B-D).Capsules normally have 5-12 locules with the numbers 6-10 being the most common.A larger locule number of 14 or 15 was reported by Salm Dyck (1849), but this could not be confirmed.As pointed out before, the num ber of locules is often not stable in Machairophyllum.
Valves are broadly to narrowly triangular, depending on the locule number.3.0-6.6mm long, basal width 3.5-6.0mm.shortly and narrowly winged with the exception of M. brevifolium; wings taper apicaily with their ends drawn out into slender tips which are connate with the awns of the expanding keels; expanding keels ± parallel at the base and close to each other and diverge to some degree in their distal part, serrate or lacerate on their inner margin, though sometimes minutely so; tips are slender awns. 1 -2(-3) mm long which nearly reach the tip of the valves.These awns are generally cohering and frequently cross each other.In M. brevifolium the awns are shorter or hardly developed.Covering membranes number of sepals sepal length (mm)  are concave in M. albidum (Figure 14B), whereas in M. bijliae and M. brevifolium (Figure 14C, D) they are roof like in shape, ± translucent and rather stiff in texture.In the latter species, they do not cover the locules entirely and are somewhat short.In fact, M. brevifolium is quite distinct from other Machairophyllum species in its fruit morphology: the expanding keels are thick, without awns or wings, closing bodies are reduced to tiny knobs and the fruit is consistently six-locular.In the other species, closing bodies are small and frequently deep-set.Their shape varies from rotund to kidney-shaped.In one speci men they were found to be slightly two-lobed (Kurzweil 1919).Although fruit morphology has been considered as the most important complex of characters for the delimitation of genera in the Mesembryanthemaceae, this does not seem to be the case in the current interpre tation of the genus Machairophyllum.

Seeds
The micromorphology of 29 specimens was examined in the present study.Seeds are pear-shaped with a pro truding micropyle which conforms with the seeds of other Mesembryanthemaceae (Figure 15A) (Hartmann & Golling 1993), 0.87(0.73-1.00)x 0.64(0.44-0.77)mm, dark brown to light yellowish brown.In the central seed portion the testa cells are predominantly elongate with a strongly convex periclinal wall and have irregularly undulating anticlinal walls (Figure 15B-E); neighbour ing cells almost touch each other.Very rarely, the anticli nal depressions between the cobblestone-like convex testa cells are rather wide.The outer periclinal wall is normally smooth to slightly verrucose.In Desmet 2158 most of the periclinal surface is smooth but the marginal areas are rough (Figure 15D).The periclinal walls of the testa exhibit epicuticular formations of various density and shape.Epicuticular formations mostly consist of minute, loosely or densely arranged rodlets (Figure 15E-G), but flake-like epicuticular formations also occur (e.g.Desmet 2158; Kurzweil 1901) (Figure 15D).The occurrence of spinulose rodlets was reported in Mesembryanthemoideae and a few genera of Ruschioideae (Bittrich 1986;Ehler & Barthlott 1978).A crystal of unknown nature and function was found on the testa just above an anticlinal wall (Figure 15F).

Pollen
Pollen was examined in 33 air-dried specimens and proved to be uniform (Figure 16).Pollen grains are tricolpate which is the common condition in the family (Dupont 1977), equiaxial to strongly longiaxial, average equatorial diameter 14.80 |jm; average of the polar dis tance 15.36 pm.The comparatively small size observed (compare with e.g.Dupont 1977 andChesselet et al. 1998) is probably the result of hydration state.The sur face of the pollen grains is microspinulose as in the majority of Mesembryanthemaceae (Hartmann 1991), and the size and density of spinules is subject to slight variation in the genus.Irregular perforations through the tectum are visible in all specimens (Figure 16C).In M. brevifolium (Lategan 2367/36) these are rather prominent and the pollen is thus approaching a reticulate condition.

Phytogeography and ecology
All confirmed collections of Machairophyllum come from the southern parts of central South Africa (Western and Eastern Cape) the only area that the genus is known from with certainty (Figure 2).The distribution range is in the Little Karoo from Barrydale eastwards and in the adjacent mountain ranges of the Swartberg in the north and the Langeberg in the south, and stretches further to Oudtshoom, Uniondale, the Baviaanskloof and Kouga Mountains and to Salt Pans Nek (near Jansenville); it is also known from the Zuurbei^ (near Kirkwood north of Port Elizabeth) which is the easternmost occurrence of the genus.Unfortunately many of the older herbarium collections indicate only the district where they were found and their exact locality is therefore unknown.Populations are rather localized w ithin the distri bution range, but in some areas this may be the result of the lack of suitable habitats or of low collecting activity.Specimens referred to Machairophyllum were also collected in Port Elizabeth, near Mossel Bay. in De Hoop Nature Reserve near Bredasdorp and near Laingsburg.but these were later correctly identified as belonging to different gen era.In addition, there is also a record from the Richtersveld of Northern Cape but this isolated occurrence needs confir mation (Figure 2).This spectacular collection was made near Lekkersing about 10 years ago (Vn iers s.n" NBG.hort.)some600 km from the well-known distribution area of the genus and also in an area where the preferred habitat of Machairophyllum is scarce.No plants were later found despite an extensive search in the area (E.van Jaarsveld pers.comm.).The unbranched inflorescences, the short bracteole sheaths, as well as the number of sepals and locules suggest that the plant belongs to M. bijliae.Another locality in Northern Cape, situated in the Vanrhynsdorp District, was shown on the distribution map of Machaimphyllum present ed in Herre (1971: 198) but no comment on the origin of the information was made (Figure 2).However, the occurrence of Machaimphyllum in Northern Cape w ould not be too sur prising.as up to the 1930s 'Little Namaqualand* was thought to be the distribution area of M. albidum (see below).
Machairophyllum albidum occurs in the western part of the distribution area of the genus, ranging from Barrydale to around Oudtshoom.An outlying locality is known near Klaarstroom in the eastern Swartberg.The widespread M. bijliae is known from the George and Oudtshoom Divisions eastwards to the Zuurberg.The distribution areas of these two species overlap in the Oudtshoom District.M. brevifolium has so far only been recorded in the red conglomerate hills between Oudtshoom and De Rust, and M. stayneri is only known from the Zuurberg.
In the past there was considerable confusion around the distribution of Machairophyllum.Linnaeus (1762), when describing Mesembryanthemum albidum (now Machairophyllum albidum) gave its locality as 'Habitat in Aethiopia' which merely implied that the plants came from Africa.Sonder (1894), in his account in Flora capensis, quoted Namaqualand as the distribution area of the sole Machairophyllum species known at the time, M. albidum (as Mesembryanthemum albidum).Sonder cited two collections, one made by A. Wyley and the other by Drege.The former collection was examined by Mrs L. Bolus who provisionally referred it to the genus Cheiridopsis (Bolus 1960: 156 [in the footnote]).The latter could not be traced in the present study, and there fore it cannot be ruled out entirely that it is indeed a species of Machairophyllum.Several subsequent authors quoted the distribution 'Namaqualand' for M. albidum or the entire genus Machairophyllum (e.g.Berger 1908;Jacobsen 1935).However, both Berger and Jacobsen probably merely adopted the distribution given by Sonder.All subsequent collections of Machairophyllum were only made in the southern part of central South Africa, and therefore the occurrence of Machairophyllum in Northern Cape was increasingly doubted (Schwantes 1957: 93).
Machairophyllum albidum and M. bijliae are most commonly found on rocky outcrops (Figure 1A, B), on bare rock on N-exposed slopes and on rocky ridges in mesic to dry fynbos or in renosterveld, commonly also where fynbos and renosterveld meet.On one herbarium collection a fynbos-valley bushveld mix is also given.The occurrence of Machairophyllum in comparatively moist fynbos is rather atypical in the family, as most Mesembryanthemaceae are found in arid or semi-arid areas in southern Africa, although this unusual habitat is also that of a few other genera (e.g.Erepsia, Carpobro tus).The few accurate collector's notes available indicate that the species grow in rocky soil and bedrock derived from TMS.The plants rarely occupy grassy habitats amongst rocks over deeper soils (mainly in Eastern Cape) and are then nearly hidden in tall vegetation (Figure 1C).No accurate ecological information is given on the type sheet of M. stayneri, but the area where the species was collected generally falls in the Savanna Biome (Rutherford & Westfall 1994) although fynbos and renosterveld occur at higher altitudes in this area.M. brevifolium is only known from the red conglomerate hills near Oudtshoom where it grows in fields of pebbles interspersed with small shrubs.
Altitudes for the genus range from 330 m in the Little Karoo to just below 1 600 m in the Swartberg.M. albidum is usually found at low altitudes ranging from 330 to 600 m.M. bijliae is very much a high-altitude species, with almost all collections made between 800 m and 1 560 m (top of Swartberg Pass).The only exception is a collection of this species made at 570 m near Joubertina (Fourcade 2384\ BOL).The type locality of M. bre vifolium is between 550 and 600 m.
Flowering in Machairophyllum albidum and M. bijli ae is often stimulated by burning of the habitat, which has been observed during the present study and has also been reported before (J.Vlok pers.comm.; notes on a herbarium sheet of M. albidum, Blackburn s.n., BOL63638).The fact that veld fires have a profound effect on the flowering of plants in the Cape Floristic Region is well documented in other families (e.g.Amaryllidaceae, Iridaceae, Orchidaceae), but is not known in Mesembryanthemaceae.However, other effects of veld fires on mesembs have been reported (e.g. the rapid spreading of Erepsia species in response to burning: Liede 1989Liede , 1990;;Hartmann 2001).Plants of Machairo phyllum are normally not seriously damaged by veld fires.Most plants grow in rocky sites where the fire intensity is low.Dense clump formation ensures that only the outer leaves are singed during the burning and most adult individuals therefore survive the fire.Furthermore, the seeds of the previous season are well protected by the comparatively hard and robust capsules, and plenty of seed is therefore available in the post-fire environment.Flowering in M. brevifolium is apparently not stimulated by burning.

Phylogeny
Machairophyllum in its current delimitation is fairly uniform in vegetative, floral and several capsule features which seems to suggest that it is indeed a natural group.At present, the genus can be diagnosed according to the following characters: clump-forming habit without visi ble stems: smooth and dotless and often waxen leaves of a green or whitish green colour; large yellow flowers which are open in the afternoon, evening or at night: absence of filamentous staminodes; long filiform stig mas: capsules with raised sutures and reflexed valve rims: covering membranes present: closing bodies small: expanding keels serrate or lacerate and apically ± awned.However, in a strict sense the morphological and ana tomical data obtained here are considered insufficient as a basis for a sound phylogenetic analysis, as a definite synapomorphy for the genus cannot be identified at this stage.We therefore suggest that further data be obtained for the entire Bergeranthus group, including molecular ones, to resolve the phylogeny of Machairophyllum.While M. albidum and M. bijliae are fairly similar in details of the internal capsule structure (valve wings pre sent: covering membranes complete: high and variable number of locules), M. brevifolium deviates somewhat (valve wings absent: covering membranes incomplete: low and stable number of locules) thus leaving doubt regarding its systematic position.Nevertheless, until new data become available.Machairophyllum is retained in its current delimitation for practical reasons despite the distinctness of M. brevifolium and we consider it prema ture to require that genera in the mesembs be defined on the basis of synapomorphies.Gartner-Zeitung 42: 187 (1927);Bolus: 155-158 (1960) (synopsis).Type species: Machairophyllum albidum (L.) Schwantes.

Distribution, habitat and biology
The species is mainly known in the Little Karoo from Barrydale to the George and Oudtshoom Divisions which is the western part of the distribution area of the genus.On Cloetespas near Herbertsdale, the species extends over the coastal mountain range.M. albidum has also been collected near Klaarstroom in the eastern part of the Swartberg (Burger BOL38796, BOL) which is an outlying occurrence of the species (Figure 2).M. albidum grows in fynbos and renosterveld.mostly asso ciated with rocky habitats, from 330-600 m.

Similar species
Vegetatively Machairophyllum bijliae is largely iden tical to M. albidum which also occurs in the same type of habitat although M. bijliae frequently has shorter leaves.In the flowering stage the difference is immediately obvious, as M. bijliae consistently has solitary flowers.
whereas inflorescences of M. albidum are branched.On average M. bijliae has also slightly smaller flowers with shorter petals.M. bijliae differs further by mostly having shorter bracteole sheaths, a higher number of sepals, and ovaries with fewer locules.While the centre of distribu tion of M. bijliae is further east, the distribution areas of the two species overlap in the Oudtshoom area.M. bijliae is always found above 800 m, whereas M. albidum is generally a low-altitude species.

Distribution, habitat and biology
The species is known only from the type collection which was made on the Zuurberg in the Eastern Cape (Figure 2).No ecological information was given on the type sheet.

Note
The only collection of this species, consisting of a complete plant and several loose fragments, was made over forty years ago.Despite an extensive search by the first author, no plants could be located.The number of sepals and locules associated with short bracteole sheaths and branched inflorescences suggest that the species is distinct.The branched inflorescence seems to point to a close relationship with Machairophyllum albidum.Alternatively, the short bracteole sheaths as well as floral characters may indicate affinities to M. bijliae.

Distribution, habitat and biology
This is the most widespread Machairophyllum species.It is known from many collections which were made in a broad band from the Oudtshoorn Division, the Swartberg Mountains, the Willowmore District, the Baviaanskloof and Kouga Mountains and Jansenville to the Zuurberg near Kirkwood in Eastern Cape (Figure 2).M. bijliae grows in fynbos and renosterveld.mostly associated w ith rocky habitats.Most collections were made at altitudes of between 800 and I 300 m. but one collection has been made near Joubertina at 570 m (Fourcade 23X4: BOL).The highest record comes from near the top of Sw artberg Pass at 1 560 m.

Similar species
Machairophyllum bijliae vegetatively resembles M. albidum.Differences are given under this species.

Note
The original spelling 'bijlii' is a mistake in gender because the species was named after Mrs D. van

Distribution, habitat and biology
The species is know n from only three collections made at or near the type localities of Machairophyllum brevi folium and the conspecific M. latifolium in the red con glomerate hills between Oudtshoorn and De Rust (Figure 2).In the population w hich was visited by the first author (at the Farm 'Skuinspad') ± 50 plants grew among small pebbles in rather open shrub vegetation next to the edge of a cliff.The type locality of M. brevifolium is at ± 5(K)-6(X) m altitude.A tew collections of this species were also made elsewhere, but their identity is doubtful.Bolus (1938: 126) pointed out the striking resem blance of this species to the genus Faucaria.referring to it as a possible 'connecting link".This does not necessar ily imply a close affinity in a phylogenetical sense al though a relationship of the two genera would not be very unlikely (J.Vlok pers.comm.).Machairophyllum and Faucaria were not considered as being related in the preliminary grouping presented by Hartmann (1991).However, in the new classification of Chesselet et al. (2002) they are grouped together in the Delospermeae.

Bijlia and Carruanthus
Bijlia N.E.Br is a genus ot two species known from around the Great Karoo town of Prince Albert and from kloofs on the northern slope of the Swartberg to the west ot it.A detailed explanation of the complicated nomen clature of the then sole species B. dilatata H.E.K.Hart mann was presented by Hartmann (1992).A second spe cies.B. tugwelliae (L.Bolus) S. A.Hammer was added later (Hammer 1995).The genus Carruanthus (Schwantes) Schwantes, from the Karoo near Willow more, comprises two species, C. ringens (L.) Boom and C. peersii L.Bolus.The latter species was placed in the monotypic genus Tischleria Schwantes on account of having a slightly dif ferent capsule structure, but is now also included in Carruanthus (Herre 1971;Dyer 1975;Smith et al. 1998;Chesselet et al. 2000;Hartmann 2001).
Plants of Bijlia and Carruanthus are compact and glabrous herbs like Machairophyllum.and have trigo nous leaves.In their morphology, the leaves of Carru anthus are similar to those of Machairophyllum but dif fer by having prominent teeth on the margins.Anatomi cally the leaves of Bijlia and Carruanthus are very simi lar to those of Machairophyllum.Their surface has a solid wax cover which breaks up to form platelets (Figure 17A, B).Local wax projections in the form of rodlets, granules or flakes (common in Machairo phyllum) appear to be scarce in Bijlia and Carruanthus.
Flowers of Bijlia and Carruanthus are solitary or are arranged in few-flowered cymes, the short peduncles usually hidden among the leaves.Pedicels of Bijlia are up to 10 mm long and those of Carruanthus up to 100 mm long.Both genera have five subequal to unequal sepals, linear-lanceolate petals and numerous stamens.Filamentous staminodes are absent.In Bijlia tugwelliae the nectaries are visible as raised portions of a ring (Figure 17D-F) which is also the situation in Machairo phyllum.Capsules of Bijlia and Carruanthus are fivelocular, and have strongly raised sutures.In Carruanthus these have reflexed valve rims which is shared with Machairophyllum.In contrast, the rims are erect and straight in Bijlia.While the capsule opens up. in Bijlia the valves separate only slightly from each other, where Seeds are ovoid to pear-shaped and ± 0.6-0.9mm long.In both Bijlia species the testa cells are extended into papillae (Figure 17G), and have epicuticular formations in the form of granules.Seeds of Carruanthus are very similar to those of Machairophyllum in that they have elongate and strongly convex testa cells with coarsely undulate anticlinal walls (Figure 17H).Epicuticular formations in Carruanthus are also very similar and mainly take the shape of rodlets.
Concluding remarks: a similar leaf shape and anato my, elongate-pedicelled flowers, capsules with raised sutures with reflexed valve rims and short and narrow valve wings, as well as a strikingly similar seed ultra structure mark clear affinities of the genera Carruanthus and Machairophyllum and suggest that the two are sister groups.The small size or absence of closing bodies in both Carruanthus species and the lack of a complete covering membrane in one (C.peersii) is probably the result of reduction.

Cerochlamys
Cerochlamys N.E.Br comprises three species in the Swellendam.Oudtshoom and Laingsburg Districts in Western Cape.A fourth species was recognized by Hartmann (1998b) but was referred to the genus Acrodon N.E.Br (Burgoyne 1998).The following brief comments refer to the actual examination of C. pachyphylla (L.Bolus) L.Bolus, while information on the other species was largely obtained from the literature (mainly Hart mann 1998b).
All three species are compact and nearly stemless succulents with smooth, clavate or trigonous leaves.The leaf surface of Cerochlamys pachyphylla and C. gemina (L.Bolus) H.E.K.Hartmann has a solid wax cover which breaks up to form platelets (Figure 17C) which also occurs in C. trigona N.E.Br (Hartmann 1998b).In C. pachy- phylla (Kurzweil 1905) the main leaf vascular bundles was found to be strongly curved or concentric with col lenchymatic sheaths.
The short-pedicelled flowers of Cerochlamys are soli tary or arranged in few-flowered cymes.Flowers are pink, purple or white, and are open during the day.Cerochlamys has mostly five subequal to unequal sepals (except six in C. gemina), linear-lanceolate petals and numerous erect stamens in a cone.All species have white filamentous staminodes.Nectaries were reported as sep arate (Herre 1971) and as '... very broad, touching each other, sometimes apparently in a ring' (Hartmann 53).The stigmas of the three species are comparatively short.Capsules are five-locular in C. pachyphylla and C. trigona, but six-locular in C. gemina.In C. pachyphylla the sutures on top of the capsule are strongly raised, and have straight valve rims.Valves are erect in the opened position and lack wings.The roof-shaped covering membranes are complete.Expanding keels are diverging and terminate in long awns.Closing bodies are absent in Cerochlamys although the placenta ends are often knob shaped (Hartmann 1998b).Seeds are ovoid to pearshaped and ± 0.6-0.9mm long.The isodiametric to elon gate testa cells are extended into papillae (Figure 171).
Concluding remarks: floral and fruit characters of Cerochlamys, particularly, the filamentous staminodes, the short stigmas, its flowering phenology with diurnal pink, purple or white flowers are very unusual in the Bergeranthus group suggesting that the genus may not be correctly placed here.While resolving the correct taxonomic position of Cerochlamys is obviously beyond the scope of the present paper, the genus is here not con sidered as part of the Machairophyllum complex.

SPECIMENS EXAMINED
Herbarium abbreviations in accordance with the latest version of Index Herbariorum, BOL* = Pickle collection at BOL; NBG = National Botanic Garden Kirstenbosch, SUG = Stellenbosch University Garden.
, Northern Cape, Gauteng and Namibia.Most genera of the Bergeranthus group share a similar pollination syndrome-with Cerochlamys as the only exception, all have yellow flowers which are open in the afternoon, evening or at night.
FIGURE 11.-Diagrams showing sepal and petal characters in M achairophyllum.Plotted measurements in B-D repre sent average values found in examined flowers.A, num ber of sepals; B, relationship of sepal length and width; C, relationship of petal length and width; D. relationship of sepal length and petal length.

pachyphylla Leaf surface, wax layer (Kurzweil 1905) mostly smooth and with breaking up into breaking up into breaking up into local projections in the platelets platelets platelets form of rodlets Inflorescence, length in relation longer longer shorter shorter to the leaves Flowers colour yellow yellow yellow pink, white Flowers, time of the day afternoon till morning afternoon
Valve wings are absent in Bijlia but are developed as short and narrow flaps in Carruanthus.The covering membranes are complete in Bijlia and Carruanthus ringens but are only developed as a small limb in C. peersii.Closing bodies are large, white bulges in Bijlia but are small or absent in Carruanthus.The general shape of the seeds of Bijlia and Carruanthus does not differ markedly from that of Machairophyllum.