Euphorbia gummifera . A . gregaria and a new species from Damaraland

I'he identity o f Euphorbia gununijera Boiss. and E. gregaria Marl, is discussed and a new species, E. damarana Leach, is described. A key to the species including E. carunculifera Leach from southern Angola and a m ap showing their distribution are provided. The possible significance o f these species in the phylogeny of the genus is also discussed. Some morphological deviations from the norm for the genus might, at first, seem to justify the exclusion of Euphorbia gummifera Boiss. E. gregaria Marl, and E. damarana Leach (described on p. 000) from Euphorbia. The most important deviations are found in the relatively large, 3 6-merous, fleshy fruits with delayed modes of dehiscence and, in E. damarana, a relatively thick, hard, woody septate endocarp; this species also lacks the usual partial parti tions at the base of the inside wall of the involucre. However, some at least of these deviations are to be found in other quite different and apparently scarcely related species which are, and it seems correctly, universally accepted in Euphorbia, for example, the large, 3-6-locular, fleshy fruits of E. virosa Willd. and delayed patterns of dehiscence in such widely divergent species as E. monteiri Hook, f., E. lathyris L. and an as yet undescribed geophyte from Zambia. In view of this and the apparently close affinities existing between the three species under discussion and such species as E. hamata Sweet, E. gariepina Boiss. and E. tirucalli L., 1 have little or no hesitation in accepting them as belonging in Euphorbia as presently constituted. Of some historical interest in this connection are a letter signed by Radlkofer and a note by Pax which are attached to a specimen of E. damarana ( Rautanen 208) in the herbarium of Zurich University. In the former, Radlkofer (replying, it seems probable, to Pax) makes the point that the 5-locular fruit does not necessarily exclude Rau tanen 's plant from F.uphorhiaceae, but he nevertheless refrains from offering any suggestion regarding its correct generic placing. According to Pax's note the material is excluded from Euphorbia by its anastomosing laticiferous ducts. However, Boodle & Fritsch (Solcreder's Systematic Anatomy of the Dicotyledons, 1908) question the accuracy o f Pax's concept of the laticifers, and their doubts seem to receive justification in sub ­ sequent literature, from which it appears that no anastomoses arc known in the non-articulated laticiferous cells which occur in Euphorbia. These three species, together with E. carunculifera Leach from southern Angola, appear to form a closely related group which may be of considerable importance in relation to the phylogeny of the genus, fhe dioecious habit and multilocular fruits (“ mult i-" in the context of Euphorbia) of these species are among characters usually considered to be primitive and it may be significant that these and similar * c /o National Herbarium, P.O. Box 8100, Causeway, Salisbury, Rhodesia. assumedly primitive traits are by no means uncommon in the same general geographical area (the Namib and its environs). One is prompted to ask whether these characters have in fact survived because o f suitable environmental conditions or have developed in response to these factors, as have geophytes and other life forms; certainly it seems probable that delayed dehiscence (not considered to be primitive) may be an adaptation to prolonged drought periods and appears to be directly comparable to the arrested development of the follicles in Stapelieae. It may also be noteworthy in this connection that several taxa possessing assumedly primitive characters (e.g. E. virosa, E. damarana and E. carunculifera) are often closely associated with Welwitschia. Although apparently forming a distinct evolutionary group, no attempt is made at this stage to fit these species into the formal nomenclature o f the subgeneric hierarchy, as it is considered that this should be left in abeyance until a much larger proportion of the species, their distribution, variation, synonymy etc. are known in greater detail than at present. Many species are still to be described, while others are so incompletely known that they are little more than names, of which even the identity is, in some instances, still subject to considerable doubt; whole areas, particularly in Africa, are virtually unknown euphorbia-wise and many important aspects (e.g. palynology), especially in relation to the succulent spccies, remain almost entirely unstudied. It is felt that any formal classificatory decisions reached on such inadequate information add nothing to our knowledge and lead almost inevitably to unnecessary nomenclatural complication and instability. In large areas of their respective distributions, which extend from just south of the Orange River to north o f Benguela in Angola, these gregarious plants form large colonies in which they are not only the dominant but often almost the only perennial species. The colonies sometimes extend for many kilometres and often determine the character of the vegetation over

assumedly primitive traits are by no means uncommon in the same general geographical area (the Namib and its environs).
One is prompted to ask whether these characters have in fact survived because of suitable environmental conditions or have developed in response to these factors, as have geophytes and other life forms; certainly it seems probable that delayed dehiscence (not considered to be primitive) may be an adaptation to prolonged drought periods and appears to be directly comparable to the arrested development of the follicles in Stapelieae.It may also be noteworthy in this connection that several taxa possessing assumedly primitive characters (e.g.E. virosa, E. damarana and E. carunculifera) are often closely associated with Welwitschia.
Although apparently forming a distinct evolutionary group, no attempt is made at this stage to fit these species into the formal nomenclature of the subgeneric hierarchy, as it is considered that this should be left in abeyance until a much larger proportion of the species, their distribution, variation, synonymy etc. are known in greater detail than at present.Many species are still to be described, while others are so incompletely known that they are little more than names, of which even the identity is, in some instances, still subject to considerable doubt; whole areas, particularly in Africa, are virtually unknown euphorbia-wise and many important aspects (e.g.palynology), especially in relation to the succulent spccies, remain almost entirely unstudied.It is felt that any formal classificatory decisions reached on such inadequate information add nothing to our knowledge and lead almost inevitably to unnecessary nomenclatural complication and instability.
In large areas of their respective distributions, which extend from just south of the Orange River to north of Benguela in Angola, these gregarious plants form large colonies in which they are not only the dominant but often almost the only perennial species.The colonies sometimes extend for many kilometres and often determine the character of the vegetation over vast areas.
Vegetatively the four species are very similar in appearance and from a distance are scarcely to be distinguished from one another.However, in fruiting characteristics they are very distinctive and their distributions are sufficiently disjunct for identifications made from minor characters usually to be reliably confirmed by the locality when only sterile material is available.A key to the species, based (1) on fruiting characters and (2) on vegetative characters follows: Gregarious, dioecious, unarmed shrubs, 1-3 m high with distinctly ribbed or terete, rod-like branches and branchlets.
(1) Key to species based on fruiting characters  Difficulty may sometimes be experienced in the identification of leafless sterile specimens when branches become shrivelled in the course of drying, as a pattern of decurrent wrinkles, somewhat similar to that of the ribs in E. gummifera, sometimes appears, especially in specimens of E. gregaria.It has, unfor tunately, not been possible to find a " key" character to cover such instances.
The shrubs are the smallest of the group but are more freely rebranched than those of either of its relatives; from both of these it differs in its smaller cyathia, differently shaped, very much smaller, 3_4-lobed capsules and smaller seeds, while its hard, woody, darker coloured, ribbed branches and branchlets, which are usually decurrent at their junctions, are quite different from the terete, more rod-like branches of E. gregaria and E. damarana.
Plants appear generally to be unisexual but the remains of an involucre attached to a partially dehisced capsule (Giess et al 5371) bears a number of pedicels surrounding the ?pedicel; from this it seems that at least some individuals may be bisexual.The capsules appear to separate first between the lobes, while dehiscence appears often to be either very retarded or perhaps sometimes incomplete, judging from the detached (or ready to fall) capsules found at the Haalenberg locality.The nauseous odour mentioned by Marloth was not noticed and it is thought that this may prove to be of a seasonal nature.
A specimen with prominent leaf bases, originally collected at Haalenberg, S.W. Africa, cultivated at Kirstenbosch, NBG 1781/27, "young branches pubes cent" .shows the relationship with E. hamata Sweet and E. gariepina Boiss. in its atypical attenuated twigs, even more clearly than in normal wild specimens.Plant an unarmed, unisexual, rounded shrub averaging about 1,5 m in height, densely branched from the base and rather less densely, alternately branched above, with the ultimate branches and branchlets 6-12 mm in diam.Branches ascending, erect, terete, neither ribbed nor striate in the live state, fibrous and tough, with a succulent, greyish green bark, usually somewhat tawny-tomentose towards the apex, especially on younger parts.Leaves caducous, sessile, narrowly obovate, subacute, rather fleshy, densely tomentose, strongly recurved, usually somewhat channelled, ±7 mm x2,5 mm-Inflorescence a densely tawny-tomentose cluster of very shortly pedunculate cymes, terminally or laterally produced on or towards the apex of the branches and branchlets; bracts broadly ovate, rather fleshy; peduncles and cyme branches stout, up to ±4 mm long (usually less), all densely tomentose.Male cyathia usually crowded, deciduous; involucre glabrous inside, cupshaped, ±3 mm deep, 6-6,5 mm diam.including the glands; glands 5, distant, fleshy, spreading, sometimes slightly deflexed, more or less semicircular, lightly rugulose on the glabrous upper surface, 1,5-2,0 mm wide; lobes 5, erect, more or less subquadrate, irregularly truncate or coarsely dentate, ±1,5 mm wide.Male Jiowers ±60, arranged in 5 fascicles opposite the lobes and closely grouped around an aborted female flower borne on a short pentagonal pedicel; fascicles each subtended on the inside by a pair of more or less obovate cuneate, relatively fleshy, tomentulose woolly bracts about 4 mm long; bracteoles numerous, mostly filamentose or a few membranous, more or less cuneate, ±3 mm long, and rather woolly at the more or less truncate apex; pedicels glabrous ±3 mm long; filaments ±1 mm long and with the anthers glabrous.Female involucre densely tawny-tomentose, narrowly obconic, truncate at the base, ±6 mm diam.including the glands, ±5 mm long, otherwise more or less as in the male.Ovarv densely tomentose, more or less ellipsoid or ovoid, very soon exserted from the involucre on a stout pedicel; ovule suspended under the cross section varying somewhat, dependent on the number of locules, ±7 mm long, 6-6,5 mm wide, 5-6 mm thick, brownish cream or creamy brown with darker patches and markings and a dark brown suture.( E. gregaria is widely distributed, mainly along the Fish and Orange rivers and usually more than 100 km from the coast.Large numbers are to be seen to the west of Seeheim, often associated with E. virosa Willd., and frequently forming large colonics in which it is the dominant species; eastwards its distribution extends as far as Kakamas, plants being common on both sides of the Orange River.

Euphorbia gregaria
It was feared that the large numbers of plants to be inundated at the site of the Naute Dam to the south-east of Seeheim might so taint the water (toxicity tests had been made at Onderstepoort) as to render it unsuitable for human or animal con sumption.However, further tests carried out by Dr M. Wolf at the Veterinary Diagnostic Centre, Windhoek, disclosed that no such effect was evident, even at 20-25 times the concentration expected.It is thought that the two related species may also be similarly innocuous since no irritating effects on the mucous membranes, such as smarting nostrils, have been noted despite extensive handling of both dry and living specimens.
In habit E. gregaria most closely resembles E. damarana but is rather more freely rebranched above and of a somewhat smaller stature, while its densely tawny tomentose inflorescence and leaves, which are strongly recurved and lack the characteristic dark glands at their base, are both quite different from those of the Damaraland plants.When in fruit E. gregaria is immediately distinguished from either of its congeners by the long deflexed pedicel on which its large rather fig-like fruits are borne.In addition to being far exserted from the involucre these fruits are very much larger and differently shaped from those of E. gummifera, from which the inland species is further distinguished by its terete (not ribbed) branches and branchlets.Production of fruits and seeds appears to be very erratic and is thought probably to be dependent on seasonal conditions.Euphorbia damarana Leach, sp.nov.Euphorbiae gregariae Marl, affinis sed folia anguste elliptica, fere glabra, haud recurva nec canaliculata; glandulis nigris stipulaneis basi foliorum bractearumque instructa; cyathiis masculis usque ad duplo grandioribus et pedicellis bracteolisque tholum prominentem formantibus; glandulis transverse oblongis saepe contiguis; capsula brevissime ex involucro exserta, loculis 4-6 valde distincta.E. gummiferae Boiss.etiam affinis sed ab ilia (praeter capsulam breviter stipitatam) characteribus simillimis atque aliis statim dignoscenda.
Plant an erect, unarmed, apparently unisexual, rounded shrub up to 3 m high and often as much as 6 m in diam., densely branched from the base, rather sparingly and randomly rebranched above, with the ultimate branches and branchlets 6-12 mm in diam.Branches more or less straight and rod-like, terete, neither ribbed nor striate, fibrous, and tough with a succulent bark (occasionally grazed, a short tuft of fibres then being left at the apex), pale yellowish green, often somewhat whitish from the resinous deposit on the surface, very slightly rough to the touch, glabrous or rarely slightly yellow'ish tomentulose on very young apical new growth.Leaves apparently fleeting, sessile, narrowly elliptic, subacute, up to 9 mm long x3,5 mm wide (in cult, up to 22 mm x8 mm), almost glabrous or sometimes with a sparse tomentum, erect or spreading (when erect with a peculiar incurved set to the base), with a dark gland (presumably stipular in origin) on each side at the base.Inflores cence a cluster of very shortly pedunculate cymes, terminal on the branches and branchlets or occasionally on short lateral flowering spurs; bracts scale-like, more or less broadly ovate, about 1 mm long, red-brown, often with a dark gland on each side at their base; peduncles and cyme branches short ( ±2 mm) and stout, glabrous or sometimes yellowish tomentose.
Male cyathia deciduous; involucre yellowish tomentose, shallowly funnel-shaped, ±4 mm long with the basal portion solid and somewhat stalk-like, 6-9 mm diam., including the glands; glands 5, fleshy, transversely oblong-elliptic, usually slightly crisped on the margins, about 3-4 mm x2 mm, contiguous or separate, usually strongly deflexed so that the upper surface is turned outward; lobes 5, tomentose, transversely oblong, ±2 mm wide, erect, irregularly truncate or coarsely toothed at the rather woolly apex; male flowers numerous, intermingled with a dense mass of woolly bracteoles, which with the pedicels eventually form a prominent woolly Plants at the type locality, ± 64 km west of Khorixas (Welwitschia), ± 2 m high.dome, arranged in 5 fascicles, not separated by partitions or pockets on the inside of the involucral wall but each subtended on the inside by a bract formed from partially united bracteoles; the fascicles are closely grouped around what appear to be the vestiges of an undeveloped female flower.Female inflorescence similar to the male but with fewer, more frequently tomentose peduncles and cyme branches; it is seldom that more than one or two capsules reach maturity (4 seen only once); involucre yellowish tomentose, somewhat urceolate, ± 6 mm long, 6 mm diam.including the glands, ± 3 ,5 mm diam.at the base of the 3,5 mm long, solid basal portion (this solid portion, similar to that in the male involucre, is here treated as being part of the involucre in view of the supporting bracts at its base; however, it could perhaps be considered as being integral with the cyme branch as in some instances there are traces of a junction with the base of the involucral cup); glands 5, fleshy, dark coloured or perhaps sometimes yellow, transversely oblong-elliptic, 2-2,5 mm wide, ±1,5 mm long, spreading to strongly deflexed, slightly crenulate and crisped on the margins, usually separate; lobes 5, more or less as in the male cyathiuni but densely tomentose inside and out; bracteoles filiform or somewhat spathulate, densely woolly at the apex, ±2 mm long, closely arranged around the ovary.Ovary ovoid, yellowish tomentose, very soon partially exserted from the involucre.Styles, equal in number to the locules of the ovary, very stout, ± 1 ,5 mm long, free almost to the base, spreading recurved, deeply grooved down the inner face, much dilated at the divergently bifid, rugose apices.Capsule subspherical, slightly angular, yellowish green, tomentulose, more densely so towards the base, averaging 20 mm diam.x 16 mm high, 4-6-locular, with a relatively thick, hard, woody, 4-6 septate endocarp, very tardily dehiscent, perhaps sometimes incompletely so, opening first between the locules with the styles persistent, very shortly exserted from the involucre on a stout, tomentose pedicel about 4 mm long; perianth rudimentary or lacking.Seed more or less oblong-ovoid, with a central depression at the truncate base, slightly obliquely truncate at the broadly subacute apex, somewhat 3-angled in crosssection from being compressed on each side of the suture, up to 8 mm long, 6,5 mm w idex5,5 mm thick but varying somewhat depending on the number of seeds in the capsule and the degree of compression to which they were consequently subjected, smooth, brownish cream to pale brown with a dark brown suture and blackish brown blotches on the flattened areas on each side of the suture, around the apex and often at the base, with a whitish area around the hilum.
Fig. 8. This, the tallest of the three closely related species, has a distribution restricted almost entirely to desert areas to the north of the tropic of Capricorn.The southernmost record is from Tinkas Flats in the Namib Desert Park at approximately 22° 50' S; this locality is more than 300 km from the most northerly known for E. gummifera and almost as distant from the nearest recorded occurrence of E. gregaria.
The main concentration known to me lies on the southern side of the Ugab River, where it constitutes not only the dominant species, but at the time of year when fruiting material was collected virtually the only species to be seen over a vast tract of country extending to the lower slopes of the Brandberg.At the type locality west of Khorixas (Welwitschia), colonies are rather smaller but again the species is dominant where present.Regeneration at both localities appeared to be very poor, but fruits with apparently viable seed were produced in large numbers in July 1973; it would therefore be interesting to learn the seedling and subsequent juvenile position in the following few seasons.
E. damarana appears to be most closely related to E. gregaria but differs, most significantly, in its shortly pedicelled, often 6-locular fruits with hard woody endocarp and larger seeds.The almost glabrous erect leaves of E. damarana are quite different from those of E. gregaria, in that species heavily tomentose and strongly recurved, while the dark stipular glands at the base of the leaves and bracts allow most (even sterile) specimens to be distinguished from similarly sterile material from either of its close relatives.The larger male cyathia with bracteoles and pedicels forming a prominent woolly dome, and transversely oblong, often contiguous glands are also characteristic of the new species.A relationship with E. gummifera is also evident but here there is much wider divergence in flowering and fruiting characters, while the ribbed, woody branches and branchlets of the smaller, more freely rebranched shrubs of the southerly based species are quite different from those of E. damarana.Affinities with E. carunculifera and E. lirucalli, albeit less close, are evidenced by the vegetative characters and gregarious colony forming habit of the former and the dark stipular glands and peculiar inflexing of the base of the erect leaves of the latter.
Ripe fruits of E. damarana, already dry and beginning to split between the locules when collected, have shown no further signs of dehiscing, their whole character, with fleshy outer covering and hard woody endocarp, being reminiscent of that of the indehiscent fruits of Elaeophorbia.

F
i g .2. E u p h o rb ia g u m m ife ra .Branch showing charac teristic pattern of three ribs decurrent from the leaf scar.

Fig. 6 .
Fig.6.-E uphorbia d a m a ra n a .

Fig. 7 .
Fig. 7.-E o p h o ro ia d a m a ra n a .Hrect, almost glabrous leaves with dark stipular glands.