Studies in the Ericoideae ( Ericaceae ) . Y . The genus Coilostigma

A revision of the genus  Coilostigma Klotzsch is presented which recognizes only two species,  C. zeyherianurn Klotzsch and C.  glabrum Benth. The genus belongs to the Ericaceae — Ericoideae and is endemic in the southern and eastern Cape Province. Fundamental differences in the ovary complement have necessitated the recognition of two subgenera,  Coilostigma and Anomalosepala E. G. H. Oliver. Aspects covered include history, morphology, phytogeography, pollination biology and taxonomy.

In Flora capensis, Brown (1906) retained the cir cum scription of the genus as applied by Bentham (1839) but ignored the sectional subdivision.He re moved the discordant C. puberulum to Thoracosperma.All these changes were retained by Phillips (1926) in the first edition of his Genera.Later, how ever (Phillips 1944), he proposed a com pletely dif ferent classification of the family in South Africa, im plem ented in the second edition of his Genera (Phillips 1951).He reduced the num ber of genera to only eight, including Erica L. This action in some cases placed totally unrelated genera together.He placed Coilostigma under Salaxis Salisb.vegetative characters are very similar in both species.
The bract is totally recaulescent in C. zeyherianurn (Figure 4,1), only very rarely partially so, and forms part of the calyx as the large abaxial m em ber in what is referred to as an unequally 4-lobed calyx.In C. glabrum, on the other hand, the bract is variable in position and with the calyx exhibits a rem arkable diversity of form.It is variably recaulescent within any one inflorescence, with the lowest whorl of flow ers having a partially recaulescent bract and the up per whorl a totally recaulescent bract.W hen the bract is partially recaulescent the calyx can be either: (1) 4-lobed with two normally sized lateral lobes (sepals) and very reduced ad-and abaxial lobes (se pals) (Figure 5,2), or (2) 4-lobed with two lateral lobes (sepals) and an adaxial lobe (sepal) and a larger less fused abaxial lobe (bract) (Figure 5,1), or (3) 3-lobed with two lateral lobes (sepals) and a slightly reduced adaxial (sepal) and no abaxial lobe (bract or sepal), or (4) 2-lobed with only two normally-sized lateral lobes (sepal), the ad-and abaxial lobes (bract and sepal/s) being absent.
As in all species of the Ericoideae with an unequal calyx the bracteoles are totally absent in all flowers.This is also the case where the bract is only partially recaulescent.
The pollen in both species occurs as single tricolporate grains with scabrate sculpturing in C. zeyherianum and no sculpturing in C. glabrum (Figure 1).
The ovary displays two distinct types.In C. gla brum it is 4-, rarely 3-locular, regular in shape and hairy with a single ovule in each locule.In C. zeyherianum the ovary is only 2-locular, flattened and gla brous.
As a result of ovary characters the fruit is very different in shape in the two species.In C. glabrum it is regular or slightly irregular with usually only one of the developed seeds being fertile.In C. zeyheria num the fruit is mostly irregular due to the develop m ent of only one fertile seed and is only occasionally 2-seeded, and regularly com planate.In both species the seed is extrem ely difficult to remove from the fruit in the dry state.This indicates that the whole flower is shed as the propagule and must disintegrate or be w etted prior to germination.
The seeds are similar in both species and are typ ically ericoid in form, i.e. spherical with a hard re ticulate testa (Figure 2).This type of seed is nor mally associated within the Ericoideae with a dehis cent capsule as in the genera Erica L., Blaeria L., Philippia Klotzsch and Ericinella Klotzsch.The indehiscent fruit and ericoid seed in this genus is shared with genera such as Coccosperma Klotzsch, Thamnus Klotzsch and Platycalyx N .E. Br. and can be regarded as a stage in the evolution of the indehiscent soft-seeded fruits found in the more 'ad vanced' genera within the subfamily.

G ENERIC DELIM ITATION AN D RELATIONSHIPS
The genus Coilostigma, as recognized in this re vision, is characterized by the possession of a totally recaulescent bract forming an unequally 4-lobed ca lyx, a 4-lobed corolla, four free stamens, bilobed anthers, single pollen grains, a 2-, 3-or 4-locular ovary with a single pendulous ovule in each locule, an indehiscent dry berry and seeds with a hard testa.
With this circumscription Coilostigma is somewhat isolated within the Ericoideae.The 2-locular 1-seeded ovary of C. zeyherianum is a character found in a num ber of genera, namely Grisebachia Klotzsch, Eremia D. Don (pro parte), Sympieza Klotzsch, Platycalyx, Simocheilus Klotzsch, Acrostemon Klotzsch and Arachnocalyx Com pton, all how ever with an equal calyx.Only in Platycalyx is there a possibility of a close relationship in that the fruiting stage is a similar dry berry with hard-walled seeds.In the other genera the evolutionary reduction has re sulted in soft-walled seeds.
The 4-celled 1-seeded ovary in C. glabrum is a character which the subgenus Anomalosepala shares with Philippia and Ericinella, both of which have an unequal calyx and hard-walled seeds but with many seeds per locule in a dehiscent capsule.It is also shared with the equal-calyxed genera Erica, Blaeria, Eremia (pro parte) and Thoracosperma Klotzsch.The first two have num erous seeds per locule in a dehiscent capsule.Eremia has a very similar ovary and fruit but flowers totally different in appearance apart from the equal calyx.Thoracosperma on the other hand has rather similar looking flowers, espe cially in T. puberulum (cf.Historical O utline), but with a fruit that contains soft, thin-walled seeds.
There is therefore no clear-cut relationship for this genus within the subfamily.It has probably been derived from some Erica-Blaeria-Philippia ancestral stock.A detailed analysis of relationships and pos sible evolutionary paths will be published when the revision of all the 'm inor' genera of the Ericoideae has been com pleted.

PH Y TO G EO G R APH Y
The genus Coilostigma is endem ic in the southern and eastern parts of the Cape Province (Figure 3) corresponding to the Langeberg and South Eastern Phytogeographical C entres proposed by W eim arck (1941).This falls within the limits of the Cape Floral R egion (W eim arck 1941;G oldblatt 1978;Oliver et al. 1983).T he extended distribution of C. zeyherianum fu rth er eastw ards to areas near A lexandria and G raham stow n m akes the genus the only endem ic one in the C ape to extend beyond the strict limits of the C ape Floral R egion as defined by G oldblatt (1978).The G raham stow n area can be regarded as a d ep au p erate relictual extension of the Cape Flora p ro p er (B ond & G oldblatt 1984).
The genus is one of only two in the Ericoideae in the Cape Floral Region with an eastern distribution, all the others having their main centres in the south w estern Cape.The other eastern genus is the monotypic Thammis.Thoracosperma is a southern genus only just represented in the south-w estern Cape by T. puberulum .
The disjunction betw een the distribution ranges of the two species (Figure 3), which is quite consider able in term s of Ericoideae in the C ape Floral R e gion, rem ains inexplicable.C. glabrum is very local ized in one population on the northern drier slopes of the low range of hills just south of the Langeberg near R iversdale.H ere it receives a fairly high annual rainfall of ± 800 mm which can be throughout the year but is mainly in the winter months.C. zeyheria num is mainly concentrated on the coastal plains in the H um ansdorp/Port Elizabeth area where it grows on sandy flats with an annual rainfall of 700-900 mm falling throughout the year.The outlying population on the coast near the mouth of the Boesmansrivier could well occur on sand as well as the inland popu lation just east of Graham stown because the latter area has flora with some coastal affinities (Jacot G uillarm od pers.comm .).

POLLINATION BIOLOGY
In the light of the findings of Rebelo, Siegfried and Oliver (1985) most of the floral features of the two species are consistent with the anemophilous syndrome: 1, the stigma is enlarged, subinfundibuliform to peltate; 2, the stamens are exserted (exserted stam ens w ere, however, found to be more generally im portant in ornithophilous and entomophilous species within the subfamily); 3, the pollen grains are small, non-sticky and easily shed; 4, there is no sign of developm ent of nectaries below the ovary, and 5, the corolla in C. zeyherianum is incon spicuous, pale yellow, soon turning brown.How ever, the corolla in C. glabrum is dark pink, a colour that could be expected to act as an attractant to in sects.
This situation is similar to that existing in Erici nella multiflora Klotzsch in which the pollen could be the reward for any visiting insects attracted by the colour of the flowers.
It is surprising that the typically anemophilous genera, namely Philippia, Salaxis, Coccosperma, Scyphogyne Brongn.and Nagelocarpus Bullock all have an unequal calyx (totally recaulescent bract) but, in contrast to our genus, they have pollen grains in tetrads.
The occurrence of anemophily in the genus was verified in the field when small clouds of pollen were seen to be em itted from the plants when disturbed.Perennial woody shrublets, single-or multi stem m ed, up to 1 m tall.Branches lacking infrafoliar sterigm ata or ridges.Leaves 3-nate, erect imbricate, ericoid, sulcate, linear.Inflorescence of 1-3, rarely 4, whorls of 3-nate small flowers at the ends of branches (mesoblasts) and lateral absolute or partial brachyblasts scattered along the mesoblasts, occa sionally clustered towards the ends into com pound heads; pedicel short, relative to the flower.Bract partially recaulescent and foliaceous in the lowest flowers to fully recaulescent in any one inflorescence or always fully recaulescent; bracteoles absent.Ca lyx unequally (2)3(4)-lobed excluding or including the totally recaulescent bract as the abaxial m em ber, lateral lobes usually slightly larger, reduced abaxial sepal sometimes present, adaxial sepal sometimes reduced or absent, sepals Vs-Vs the length of the corolla.Corolla 4-lobed, tubular to narrowly ovoid to urceolate, glabrous or hirsute, pale yellow to white, or pink; lobes short, erect to slightly spreading.Stamens 4, free, exserted or included by abortion; filaments linear; anthers bilobed, muticous, dorsifixed near the base, thecae oblong, pore Vio-lA the length of the theca; pollen grains single, tricolporate.Ovary 2(3)4-locular with a sin gle pendulous ovule per locule, transversely broadly obovate, com planate or globose, glabrous or puberulous; style filiform, exserted; stigma broad, peltate to subinfundibuliform with 2(3) or 4 stigmatic pro cesses.Fruit an indehiscent berry with a thin, rather dry, leathery pericarp, irregularly obovoid with only one seed developed from a 2-locular ovary or glob ose from a 4-locular ovary; seeds ovoid to spherical with a hard reticulate testa.
A genus of only two species, endemic in the south ern and eastern Cape Province, southern Africa.The nam e is derived from the G reek coilos 'hollow' and stigma.

KEY TO THE SU B G E N E R
A species forming erect shrublets, occurring on sandy plains near the coast from south of Hum ansdorp eastwards to Kenton-on-Sea flowering from January to D ecem ber depending on the locality.
A taxon containing two distinct varieties which occur growing together in most populations.Flower with completely glabrous corolla.Flower with pubescent to hirsute corolla, other wise as in the typical variety.Klotzsch (1838) described three species, C. tenuifolium , C. zeyherianurn and C. dregeanum, when he created the genus Coilostigma.These he based on differences in corolla hairiness, sepal shape and branch thickness.An examination of all subsequent collections has shown the sepal shape and branch characters to be continuously variable over the whole distribution range and therefore unreliable for taxonomic delim itation.
T here is discontinuity in the indumentum of the corolla where m aterial can easily be placed in gla brous or pubescent to hirsute groups.During field investigations of five widely separated populations in the Port Elizabeth to H um ansdorp area, I found that both forms did occur together to a varying degree in each population and that no interm ediates existed.I consider this type of discontinuity worthy of recogni tion at varietal level.
Even though the species is recorded as widespread on the flats it is today by no means common.Its habitat is being inundated by alien vegetation, in particular the Port Jackson Willow, Acacia saligna (Labill.)W endl., or it is being destroyed by housing estates or farming practices.In the Port Elizabeth area plants are very difficult to find nowadays in places where they must have been abundant in the past.A small population could survive in the reserve alongside the railway line in Walmer.

5
The best populations I found occurred on the flats west of the m outh of the Slangrivier south-west of H um ansdorp, but here the recently applied agricul tural practice of bush-cutting for pasturage is deci mating the species.Only on the outcrops of low sta ble dunes or in the dune slacks too small to m an oeuvre in, does the species still manage to survive and form almost pure stands.
T h e p o p u la tio n s near the m outh of the Boesm ansrivier have undoubtedly disappeared as the sandy habitat is also ideal for farming in the area.R eported populations at Slaaikraal and Coldsprings west of G raham stown could not be located.It seems unlikely that the species should occur so far inland, but D r A. Jacot Guillarmod assures me that vegeta tion elem ents with coastal affinities do occur in that area.
A species form ing com pact coppicing shrublets up to 500 mm tall; confined to a few silcrete hills near G arcia's Pass in the Riversdale area of the southern C ape Province and flowering from O ctober to Jan u ary.
This species was until recently only known from the type collection m ade in N ovem ber 1814 by B ur chell.T he population, consisting of only 24 plants on the K leinberg north-w est of R iversdale, corresponds very closely to the m ore exact locality on B urchell's specim ens 'betw een Kleine Vet River and foot of L angeberg'.T he species appears to be very rare.
T he row of hills form ing the ridge just south of the L angeberg M ountains could well have additional populations of C. glabrum on it.H ow ever, the plants are rath er inconspicuous and would seem to flower m ost profusely a year or two after a fire.B e ing copious resprouters the plants grow quickly and flower sooner than the surrounding reseeders and are then m ore conspicuous.
The species is rem arkable in the whole subfamily for the degree of variability in the form and arrange m ent of the calyx.Even within a single inflorescence the calyx may vary considerably.In the genus Sympieza the calyx may vary from 2-4-lobed in a single inflorescence, but in that genus there is no partially to fully recaulescent bract to com plicate the issue.
The above variability within the calyx is confined to C. glabrum and does not occur in the com m oner and m ore w idespread C. zeyherianurn.
M ORPHOLOGY The plants of Coilostigma are typical ericoid woody shrublets with one species, C. zeyherianurn, being single-stem m ed and the other, C. glabrum, a m ulti-stem m ed coppicing shrublet.Most of the other Botanical Research Unit, P.O .Box 471, Stellenbosch 7600.
the following herbaria are thanked for the loan of specim ens: B O L, K, M EL, M O , N B G , P, P R E , S, SAM .Discussions with A. Jacot G uillar m od of G R A are appreciated.Electron microscope investigations were carried out using the ISI 100A at the Fruit and Fruit Technology R esearch Institute, Stellenbosch, with the assistance of C. Swart and P. van der M erwe.