Studies in the Sphaerocarpales ( Hepaticae ) from southern Africa . 2 . The genus Sphaerocarpos and its only local species , S . stipitatus

A taxonomic account o f the genus Sphaerocarpos, subgenus Austrosphaerocarpos, and its only local species, S. stipi­ tatus Bisch. ex Lindenb., is presented here. These taxa are classified in the suborder Sphaerocarpineae of the order Sphaerocarpales, for which short notes and a key to all three constituent suborders, Monocarpineae, Riellineae and Sphaerocarpineae, are provided.


INTRODUCTION
The genus Sphaerocarpos (Micheli) Boehmer was first recorded from southern Africa by Proskauer (1954).He received material from the algologist, Dr M.A. Pocock, who had collected it in the Eastern Cape, on the banks of pools in the Palmiet River, a tributary of the New Years River, seven miles from Grahamstown, on the Cradock Road.Miss Lilian Britten, a lecturer at Rhodes University College, had originally discovered Sphaero carpos plants at this locality.A further collection from Clanwilliam, by Prof. E.A.C.L.E.Schelpe, was also recorded by Proskauer. Amell (1963) did not report any new collections and the only recent published South African record of the species is by Long (1993) from a 1969 collection, H.R. Toelken 1978 (BM.BOL) from Paardeneiland, Cape Town.
Seven of the collections that I studied, have not been reported in the literature before.Despite repeated visits to the Northern, Western and Eastern Cape by various collectors, m yself included, such a small number of gath erings must surely reflect the rarity of these plants, although Proskauer (1955) remarked that, 'one does not normally find members of the group in the field without being familiar with them '.Their truncated life cycle, from spore to spore, can take less than 45 days (Schuster 1992), and dramatically reduces the time period during which they are likely to be found.
It is, nonetheless, hoped that the present, fully illus trated paper, will familiarise more botanists with these remarkable plants and that, in future, they will collect them, thus enabling us to establish the local distribution range more completely.Previously, it was thought that 5. stipitatus was restricted to the southern hemisphere, i.e.Chile in South America (where the type specimen had been collected by Bertero in 1829) and South Africa.Recently, however, it was also collected as a presumed adventive in Portugal (Sergio & Sim-Sim 1989), as well as at a remote, high altitude locality in East Nepal (Long 1993), where its accidental introduction is unlikely.This paper on Sphaerocarpos stipitatus, is the second in a series of three on the Sphaerocarpales in southern Africa.

MATERIAL AND METHODS
The same procedures as outlined in Perold (1999b) were employed in the preparation of the material for examination and photography by compound light micro scope and scanning electron microscope.
Plants terrestrial, dorsiventrally flattened, bilateral, consisting of a stem (or axis), once or twice to repeated ly furcate, laterally invested with delicate, leaf-like lobes.Ventral scales absent, instead invested with ephemeral slime papillae.Cells thin-walled, lacking oil bodies.Rhizoids all smooth, hyaline.
Plants ephemeral, gregarious to scattered; stems once or twice (or more frequently) furcately branching, dor siventrally flattened, laterally invested with delicate, succubously inserted, leaf-like lobes; ventrally (and apically) with scattered slime papillae; ventrally with smooth, hyaline rhizoids.Dioicous, strongly heterothallic; gametangia individ ually enveloped by flask-shaped involucres, small in male plants, but much larger in females, which are ses sile or stipitate, wall unistratose, only exceptionally bistratose, eventually containing globose capsule and short seta with foot.Spores remaining in tetrads or separating at maturity, ornamentation reticulate or ridged.Species in the genus fall into two, well-defined groups that were recently segregated by Schuster (1992).Proskauer (1954) concluded that the specific epithet stipitatus for this species was apt, since such a stalk did not exist in any other species of the genus.The longest stalk that he measured was ± 1.5 mm.Recently, howev er, Long (1993) reported that in the material from Nepal and Portugal (Sergio & Sim-Sim 1989), 'the female flasks have an extremely short basal stalk'.The stalks I measured were also short, only 200-795 |jm in length, which would support Long's observation that, 'develop ment of the stipe must be considered variable', hence the minor alteration I made to Schuster's (1992)  Plants ephemeral to short-lived, gregarious or scat tered; stems once or twice, to repeatedly furcately branching and forming partial rosettes; markedly heterothallic, male gametophytes tiny (Figure 1A.B), anthcridial flasks purplish brown, intimately associated with much larger (x 10), light green, female gameto phytes.Stems somewhat indeterminate, in both sexes prostrate, dorsiventrally flattened, in the middle up to 260-300 pin thick, consisting of (2-)3 or 4 layers of thin-walled, 4-or 5-sided, elongated cells, 112.5-160.0x 45-75 pm, ventral cell layer with scattered slime papil lae, 37.5-62.5 x 17.5-22.5pm. raised on smaller or larg er basal cell; above m ostly obscured by crowded gametangia, each with a small or large (depending on sex) flask-shaped involucre, produced in acropetal sequence, usually in 2 series; laterally giving rise to deli cate, unistratose, translucent, alternate, succubously ori ented, leaf-like lobes; ventrally anchored to substrate by rhizoids, all smooth, hyaline, 30-50 pm wide.

DISCUSSION
The genus Sphaerocarpos has aroused much interest, because sex chromosomes in plants were first found in S. donnellii by Allen (1919).Since then, it has been repeatedly studied with regard to its genetics and cytol ogy; furthermore, a number of cultures have been main tained for lengthy periods of time.
In several aspects, the gametophyte, with its prostrate stem (or axis) and delicate, 2-ranked, succubously insert ed leaf-like lobes, resembles Fossombronia species, but so-called 'angle' leaves at the fork of dichotomies, as described by Proskauer (1954) and Schuster (1992), have not been observed by me in the present study, although I .am familiar with them from my work on the Fossombroniaceae (Perold 1999a).The gametophyte in Sphaerocarpos species is delicate and lacks physiological drought resistance (Schuster 1992); it is, nevertheless, adapted to warm and some times disturbed areas, with adequate moisture only sea sonally and with intervening long, dry periods.It is regarded as an ecological specialist and is a temporary component of vegetation that frequently endures drought in summer.To cope with such an environment, its life cycle is considerably shortened and development of the sporophyte is accelerated; it survives the dry periods as spores, which generally remain in tetrads, eventually giving rise to two male plants in close proximity to two female plants, thus ensuring that fertilisation takes place and that a new generation will ensue.
In using a m olecular approach by determ ining sequences for the 18S-r RNA gene to construct phyloge netic trees of a number of bryophytes, Capesius & Bopp (1997) concluded that the Sphaerocarpales diverged early as a separate clade among the Marchantiopsida.

Ecology
In southern Africa, S. stipitatus is restricted to the winter rainfall regions of the Northern.Western and Eastern Cape, which experience hot, dry summers (Figure 5).The plants grow at altitudes ranging from sea level to ± 1 200 m, on moist, fine-grained, sandy to clayey soils or on mud; at drainage ditches, water cours es or on earth banks; under fynbos, short karroid scrub or grass, often together with mosses and Riccia species.The localities fall in several different vegetation types, name ly Mountain Fynbos, Upland and Lowland Succulent Karoo, as well as Grassy Fynbos (Low & Rebelo 1996).Dates when sporulating material was collected, range from the end of July to early October.

ACKNOWLEDGEMENTS
My sincere thanks are extended to Dr D.G.Long for kindly refereeing this paper, to the Curator of BOL for the loan of specimens; to Dr O.A. Leistner for his valu able advice and to my colleagues at NBI for kindly col lecting specimens of S. stipitatus, and particularly, to Ms M. Koekemoer, Curator of PRE. for collecting and care fully tending live material; also to Ms G. Condy for the drawings; Mrs A. Romanowski for developing and print ing the micrographs and to Ms D. Maree for typing the manuscript.

FIGURE 2 .
FIGURE 2 .-Sphaemcarpos stipitatus.A, male involucre containing antheridium partly exposed; B, male involucre; C, archegonium and flask; D, E, older flasks; F, large flask with 2 capsules; G, c/s stalk; H, cells in outer wall o f flask (without chloroplasts).I-L, wall o f flask: I, mouth and upper part from outside; J, mouth and upper part with papilliform cells from inside; K, c/s with larger, clear outer cells and smaller, inner cells containing numerous chloroplasts; L, inner cells more enlarged M, younger capsule, with seta and foot enveloped by calyptra; N, calyptra, above with persistent archegonial neck, below covering seta and foot; O, c/s seta; F, c/s foot; Q, capsule wall with out thickenings, but covered with starch grains; Ri-Rj, nutritive cells.A-Rj, K otkem otr 1425.Scale bars: A -C , L, P, 50 |im; D-F, 500 pm; G -K , 100 pm; M, N, 200 pm; O, Q, Ri-R*, 25 pm.Artist: Gillian Condy

suborder Sphaerocarpineae Cavers lb Plants aquatic; distribution in both winter and summer rainfall regions of southern Africa; uniform in appearance, consisting o f erect stem, dorsally bearing undulate wing and small leaf scales at sides and ventrally; cells dimorphic, some with an oil body; spores single, ornamentation various
................suborder Riellineae R M.Schust.