Florence Grovida Gardening

Selaginellaceae

Selaginellaceae Willk. in Willk. and Lange, Prodr. Fl. Hisp. 1: 14 (1861); Reed, Mem. Sc. Brot. 18: 1-287 (1966); Pichi Serm, Webbia 35 : 235 (1982).

Terrestrial, or very occasionally epiphytic, usually perennial plants, of varied habit, with an erect or prostrate main stem and subsidiary branch systems of varying arrangements, the basal portions not differentiated into a distinct rhizome although some erect species spread by means of creeping basal branches known as sobols, which in turn give rise to further erect branches; growing points not protected by scales. Roots (sometimes termed rhizophores) dichotomously branched, varying in thickness, arising from the axils of branches, either throughout the length of the main stem, or basally (acting as support in erect species), or occasionally apparently adventitiously. Main stems either far-creeping and often much-branched, of indefinite growth which may be only seasonally halted or terminated; or short-creeping and then becoming erect, often with a distinct unbranched ('caulescent') region below, and with variously arranged frond-like complanate branch systems (pseudofronds) of finite growth above, further growth arising only from basal branches; sometimes exhibiting a scrambling or climbing habit. Leaves spirally arranged, ligulate, those on basal creeping portions often distantly arranged, either all similar or of two kinds, at least on the secondary and ultimate branches where they are arranged in four ranks. Strobili terminal on primary or ultimate branches, compact, or occasionally more spread out along secondary branches, apex occasionally reverting to become a vegetative shoot; or, more rarely, in a lateral position on a primary or secondary branch. Spor-

ophylls leaf-like, spirally arranged or in ranks of four, uniform or, more rarely, dimorphic, subtending sporangia which are on the adaxial surface just above the ligule; sporangia stalked, of two kinds, variously disposed throughout the strobilus, megasporangia assuming a shape dictated by the developing megaspores, microsporangia globose or slightly wider than long, thin-walled but with areas of thickened cells which aid dehiscence; megaspores trilete, usually four (>42 have been observed) in each sporangium, pale buff or white, with distinct muri or ridges around the equator and along the triradiate scar, sporoderm variously patterned, rugose-reticulate, rugose, papillate, tuberculate, granulate, rarely plain on proximal face, rugose-reticulate patterns predominate generally there is less ornamentation on the proximal face than on the distal face, 200-600 /an in equatorial diam.; microspores trilete, >100 in each sporangium, ranging in colour from yellow, through orange-brown, to red, sporoderm variously patterned from finely echinulate through papillate to verrucate, sometimes strongly rugose, 20-60 ¡jm in diam.

A family of a single genus, with some 750 species mainly in the tropical zones of the world, with a few species reaching the arctic-alpine zones in both hemispheres.

Floristic Studies. The following works by A. G. H. Alston, who made an extensive study of the genus during his tenure as pteridologist at the British Museum (Natural History), 1930-1958, give keys to Selaginella of selected areas: Africa, central (1957), West (1959), South (1939a), Madagascar (1932); America, Carribean (1952), North (1955), South-temperate (1939b), South-tropical (with Jermy and Rankin 1981); Asia, China (1934a), India (1945), Indo-China (1951), Malesia (1934b, 1935 a, b, 1937, 1940). Other useful regional accounts include Jermy (1970: E.Africa), Jermy in Parris et al. (1984; Borneo), Proctor (1985: Jamaica), Smith (1981: Mexico), Stolze (1983: Guatemala), Tagawa and Iwatsuki (1979: Thailand), Wong (1983: Malaysia).

Anatomy and Morphology. Stems are basically di-chotomously branched, with various, often diagnostic, branching patterns (Jermy 1986; Wong 1983). Vascular anatomy ranges from a relatively simple protostele (always present in young sporelings) to two steles (which in prostrate species are flattened in the plane parallel to the substrate), to more compound plectosteles of several plate meristeles (which vary from being flat in cross-section to U-shaped or a closed circle), to T- and X-shaped 'actinosteles' (Mickel and Hellwig 1969). Each stele is surrounded by a conspicuous endoder-mis. Hieronymus (1901) used the vascular complexity of the stem to delimit taxonomic sections, but Bierhorst (1971) pointed out that variations can occur in a single species depending on the position and width of stems. In many species adventitious shoots arise from the primary branch axes. The xylem in some species of subgenera Selaginella and Tetragonostachys is unique in having vessels of an advanced type which occurs elsewhere only in flowering plants. One group of predominantly tropical American species in subgen. Sta-chygynandrum (Series Articulatae Spring) have weaker areas in the cortex, usually just below the branch, which appear nodular although the vascular structure is unaltered. Very few species actually break naturally at this point and the function is unclear. Somers (pers. comm.) has studied the anatomy and morphology of this group and believes it to be a distinct and highly advanced section of the genus.

Roots (rhizophores) arise in, or proximal to, the axils of a stem dichotomy, or occasionally adventitiously on the stem surface. They are dichotomously branched, generally very smooth and cutinized externally, and in many species are stout and support the aerial stems; they are also capable of developing, under certain conditions, into a typical leafy stem and their morphogenetic origins are a matter of debate. Root steles are monarch to tetrarch, with the vascular tissue bilaterally distributed as in Isoetales, Lepido-dendrales and most Lycopodiales (Bierhorst 1971).

The leaves of Selaginella are traditionally recognized as microphylls (as in other Lycopsids) and most species have leaves with a single unbranched vein. Occasional reports indicate a more complex situation (in S. adunca A. Br. ex Hieron., Mukherjee and Sen 1981; S. schaffneri Hieron., Wagner et al. 1982). The latter discuss phylogenetic relationships. In those genera with dimorphic leaves, the lower leaves on the primary stem, especially in erect species, may appear to be uniform and only gradually change shape towards the dimorphic condition on the upper part of the stem. Leaf shape is diagnostic and is best viewed on the lower part of a secondary branch. At a branch dichotomy one lateral leaf appears in the axil of the dichotomy and is termed 'axillary leaf. It is slightly different in shape and also diagnostic. Epidermal cells with sinuous (or more rarely straight) anticlinal walls are more or less consistently isodiametric on the adaxial surface of lateral and on the abaxial surface of median leaves, and elongate on the opposing surfaces, respectively; the cells lying over the midrib may not conform. Callose deposits, which later silicify, may be observed on young leaves under fluorescent microscopy (Bienfait and Waterkeyn 1974). Such sculpturing, observed clearly under the SEM, is consistent and can be useful in the determination of species (Dahlen, pers. comm.; Jermy and Quansah, unpublished). Stomata are anomo-cytic and, for the most part, situated on the abaxial surface only, either scattered or confined to the midrib region and margin or leaf apex (Quansah, pers.

comm.; Gulyas 1961). Ligules can be aciculate-lingu-late to obclavate, ranging from 0.10 to 0.45 mm long, and are consistent within species. Horner et al. (1975) have studied the ontogeny and fine structure of the ligule but dismiss any former ideas as to function and concluded that this is still an enigma. They suggested that the ligule may be a vestigial organ which has lost its ability to function.

Strobilus Structure and Sporophyll Arrangement. In a review of 30 species of Selaginella (in subgenera Selaginella and Stachygynandruni) Horner and Arnott (1963) found three major patterns in the arrangement of sporangia in each strobilus: (1) Strobili having a basal megasporangiate zone with an upper zone of microsporangia; (2) strobili having two rows of megasporangia (occasionally with a few microsporangia) and two rows of microsporangia; (3) strobili which are wholly megasporangiate. They found a reasonable correlation with the infrageneric classification proposed by Baker (1883) but more study is required to ascertain the usefulness of sporophyll arrangement in the taxonomy and phylogeny of the genus. The initiation of heterospory occurs sometime between sporangium inception and meiosis (Horner and Beltz 1970), and its significance in phylogeny also needs further investigation.

The morphology of sporophylls reflects that of the vegetative leaves, basal megasporophylls sometimes being slightly larger than the microsporophylls higher up the strobilus. In subgen. Heterostachys the larger sporophylls (which may not always be megasporangiate) are folded, forming a lamina flap or pteryx (Quansah and Thomas 1985) which partially enfolds (and protects) the sporangium.

Somers (1982) described an arrangement of thickened cells in the sporangium wall of species in the Series Articulatae which he claims is unique to that group and was not seen in other species examined.

Store Morphology. Spore-wall formation of Selaginella and its phylogenetic significance within the Pteri-dophyta has been the subject of research by Pettitt (1966), Kempf (1970) and A.F.Tryon and Lugardon (1978). The outer walls of megaspores, composed of sporopollenin and much silica, have characteristic patterns which may have taxonomic significance; reticulate and rugose patterns predominate. Similarly, the sporoderm patterns of microspores, which may be quite different from those found on the megaspores of the same species, may show species relationships. Significant regional or systematic surveys have been published (A.F.Tryon 1949; Knox 1950; Hellwig 1969; Minaki 1984), but more are needed.

C ¡ametophytes and Embryology. There is no special mechanism for spore dispersal, spores of both kinds frequently remaining in the dehisced sporangia until the surrounding plant tissue decays. In open habitats, strong winds may help to disperse spores, but ultimately most of the spores will fall around the parent plant. In mat-forming species [e.g., S.kraussiana A. Braun, S. apoda (L.) Spring] spores of both kinds may lie dormant for long periods until the parent plant dies or is physically removed (e. g., by the foraging of an animal), when gametophytes of both sexes will germinate and produce sporelings (Webster 1967).

Gametophytes are endosporic and the prothallus is well developed when the spores are shed. The arche-gonia and antheridia are similar in structure and mode of development to those of Isoetes. Antherozoids are biflagellate and similar to those of Lycopodium. The embryology is known for only a few species and shows variation in the development of the suspensor cell and foot; a wider survey is needed to establish the taxonomic significance of this.

Phytochemistry and Pharmaceutical Uses. No extensive comparative studies have been carried out on the Selaginellaceae. Yasuo et al. (1984) studied the oligosaccharides in nine eastern Asiatic species and found significant differences. Species are collected locally in India and China and sold in the markets for medicinal purposes.

Cytology and Sporogenesis. The first reliable chromosome counts were made by Manton (1950) on three European species of Selaginella, showing 2«= 18. In an extensive survey of 76 species, Jermy et al. (1967) showed, that four base numbers exist (x=l, 8, 9 and 10 in subgen. Stachygynandrum and x=9 in subgen. Selaginella and Heterostachys), with triploids and tetraploids being found in several species with x=9. There was no correlation between chromosome base number and subgeneric classification, but with pattern of coning: those with x=9 producing cones on isolated branches sporadically, those with x= 10 coning simultaneously on all branch endings of the primary branch system or pseudofrond. The size of the chromosomes shows considerable interspecific variation, althoug all complements are very small. Subsequently n=12 has been reported (Panigrahi). Hybrids have been reported in subgen. Titragonostachys (R. M. Try-on 1955), determined by intermediate morphology and spore abortion, but the cytology was not checked.

Pettitt (1971), in investigating developmental mechanisms in heterosporous plants, showed that in the me-gasporangium of S. sulcata (Desv.) Spring (and presumably most other species) all but one of the megasporocytes either degenerate, or persist without completing the meiotic cycle, presumably as diploid cells. This situation could lead to diploid megaspores and thus agamospermy, a condition indicated by records of megasporangia with single or two spores (Ly-

on 1902; R. M.Tryon 1955). Agamospermy was also shown in the triploid S. tenerrima A. Br. ex Kuhn, a true therophyte which survives the dry season only as spores (Kornas and Jankun 1983).

Subdivision. The family is presently regarded as mo-notypic although Rothmaler (1944) resurrected the earlier generic names LycopotHoides Boehmer and Didiclis Beauv. for some European species, without any significant taxonomic revision. Kunkel (1963) published Stachygynandrum myosurus (Sw.) Kunkel [=Selaginella myosurus (Sw.) Alston] but again without discussion.

At the subgeneric level, Baker (1883) divided the genus into four subgenera and this was followed by Walton and Alston (1938). Hieronymus (1901), on the other hand, followed the arrangement of Spring (1850) and raised his Sections, Homoeophyllae and Hetero-pkyllae, to subgeneric rank, thus amalgamating Baker's three subgenera with dimorphic leaves into a single subgenus, Heterophyllum, a situation followed by Try-on and Tryon (1982). Somers (1982 and pers. comm) suggested that the Series Articulalae (subgen. Stachygynandrum) are sufficiently distinct to warrant consideration as a separate subgenus, but made no firm proposal. The group is certainly distinct and more investigation is needed. The present treatment propose five subgenera based on morphology and distribution.

Distribution, Ecology and Physiology. Subgen. Selaginella: one species, S. selaginoides (L.) Link, is a base-rich mire plant with a circumboreal range extending south to the Canaries, but absent from Africa, and in North America, south to latitude 42° N. The second species (S. deflexa Brackenridge) is endemic to bogs in the Hawaiian archipelago.

1. Tetragonostachys is composed of plants characteristic of seasonally dry areas, ranging from southern North America across the tropics in South America, Africa and the Indian Subcontinent to northern China and Japan, a few species extending to more mesophytic heathy woodlands in north-temperate areas. Those living in dry areas have thick cutinized leaves with fine hair points which protect the growing shoot apex.
2. Ericetorum: S. uliginosa (Labill.) Spring is confined to proteaceous heathlands throughout the Australian continent and two further species of similar habitats are annuals, one [5. gracillima (Kunze) Spring] in SE Australia, the other [S.pygmaea (Kaulf.) Alston] in southern Africa.
3. Stachygynandrum and subgen. Heterostach-ys: widespread in all continents; predominantly terrestrial plants of lowland to mid-montane primary rainforest but preferring more open glades and river banks, and therefore a frequent component of secondary forest in these areas. Occasionally found as epiphytes on mossy tree trunks, and some with a climbing habit [e.g., S.willdenowu (Desv.) Baker, 5. myosurus (Sw.) Alston] can soon become smothering weeds in gaps and clearings (Wong 1983). The latter species commonly displays a metallic blue tinge on its leaf surface which may act as an interference filter, increasing the transmission of light at the red end of the spectrum, those wavelengths most used for photosynthesis at the forest floor level. In addition, the leaves of this species possess epidermal cells with regular convex surfaces which may focus light on the single, large chloroplast resting at its distal end (Lee 1977). A few species reaching cooler temperate regions, e. g, S. den-ticulata (L.) Link of the Mediterranean area and 5. le-pidophylla (Hook. & Greville) Spring of Mexico, are adapted for seasonal drought by having the ability to inroll both leaves and stems to prevent excessive water loss. The leaves ot the latter and similar species, sold under the name of "Resurrection plants", can withstand repeated drying/wetting without showing lesions in the cell membranes (Leopold et al. 1981). An alternative strategy is seen in S. tenerrima A. Br. ex Kuhn, a typical therophyte from south-central Africa. This species will live only for the few weeks of the wet season and then reproduce by agamospermous mega-spores, very few, if any, microspores being formed (Kornas and Jankun 1983).
4. Ligulate, heterosporous and bispor-angiate, herbaceous plants which probably gave rise to Selaginellaceae appeared amongst the arborescent Ly-cophytes of the Lower Carboniferous. A significant fossil seen throughout the Carboniferous is Pauroden-dron, now regarded as Selaginella fiaipontii (Le-clerque) Schlanker & Leisman. It shows some Sigillar-ian characteristics but may also be compared in general morphology to the extant S. selaginoides. The majority of fossil forms of Selaginella-like plants (Selagin-ellidites, SelagineUites) have been described from me-gaspores from the Cretaceous and Tertiary sediments in the course of studies on pollen/spore assemblages. A single genus:

Selaginella Pal. Beauv. Figs. 3,13,14

Selaginella Pal. Beauv., Mag. Encycl. Paris 9 (5): 478 (1804), nom. conserv.

Description as for the family. The following subgenera are recognized here:

Subgenus Selaginella (2 species). Stems erect, new primary shoots arising from the base upon maturation of the single terminal strobilus, rooting from a basal hypocotular node; leaves and sporophylls are spirally arranged, uniform and herbaceous.

Subgenus Ericetorum Jermy, Fern Gaz. 13: 117 (1986) (3 species). Stems erect, either unbranched or more compound, arising from a creeping solenostelic stem; leaves uniform, decussately arranged at least below, more or less herbaceous; sporophylls tetrasti-chous.

Subgenus Tetragonostachys Jermy, Fern Gaz. 13: 118 (1986) (c. 50 species). Prostrate or low suffruticose plants, often mat-forming, stems much-branched, rooting throughout; leaves spirally arranged, uniform or with a tendency towards dimorphism on prostrate branches (possibly as a result of one-sided illumination), usually coriaceous, linear-lanceolate or sometimes needle-like with long hair points; sporophylls tetrastichous.

Subgenus Stachygynandrum (Pal. Beauv.) Baker, J. Bot. London 21: 3 (1883) (c. 300 species). Primary stems either creeping, branches semi-prostrate, rooting at the axils of branch dichotomies, or erect, rooting usually at the base of main stem only, suffruticose or with elaborate compound branching systems; primary and secondary branches dichotomously branched, frequently in such a way as to form a regular pseudopin-nate arrangement in one plane, pseudofronds with a characteristic outline, ultimately producing strobili simultaneously at the branch apex, or in an irregular pattern in which only the upper branches produce strobili, the lower vegetative branches becoming fertile on the maturation of the terminal one above; leaves dimorphic, at least on the secondary branches, in four distinct rows, those of the two upper (dorsal or median) rows being distinctly smaller than those of the lower (ventral or lateral) rows; leaves on erect primary stems often scarcely dimorphic; sporophylls uniform and tetrastichous.

Subgenus Heterostachys Baker, J. Bot. London 21: 4 (1883) (c. 60 species). Stems creeping and much-branched, or secondary branches erect and suffructi-cose, rooting at branch axils; leaves as in subgen. Stachygynandrum; strobili complanate, sporophylls dimorphic, tetrastichous, those on the ventral side smaller than those on the dorsal side of the shoot.

Nr. 13 A-E. Selaginellaceae. A Selaginella hordeiformis Maker, habit (xl), leaves dimorphic on base of stem. B, <' Selaginella firmuloides Warb. B Habit (x 1), leaves on stem base monomorphic. C Strobilus with monomorphic sporophylls ( x 6). D, E Selaginella kurzii A. Br. ex Warb. D Part of Hlrobilus with dimorphic sporophylls (x 10). E Part of sterile portion of stem with median and lateral leaves (x 10) (A-C from Brownlie 1969; D, E from Panigrahi and Dixit 1968)

Fig. 14 A-C. Selaginellaceae. A, B Selaginella apoda (L.) Morien. A Habit (x 1.5). B Detail of sterile portion of plant (x 12).C Selaginella myosurus (Sw.) Aiston, strobilus and vegetative branch bearing it (x 6) (A, B from Billington 1952; C from Alston 1959)

Selected Bibliography

Alston, A. H. G. 1932. Selaginellaceae, in C. Christensen, The pteridophyta of Madagascar. Dansk Bot. Ark. 7:193-200.

Alston, A. H.G. 1934a. An enumeration of the Chinese species of Selaginella. Bull. Fan Inst. Biology (Bot) 5: 2611-294.

Alston, A. H. G. 1934b. The genus Selaginella in the Malay Peninsula. Gdns' Bull. 8: 41-62.

Alston, A. H. G. 1935a. The Philippine species of Selaginella. Philipp. J. Sci. 58: 359-383.

Alston, A.H.G. 1935b. The Selaginellae of the Malay Islands I. Java and the Lesser Sunda Islands. Bull. Jard. Bot. Buitenzorg III, 13: 432-442.

Alston, A.H.G. 1937. The Selaginellae of the Malay Islands II. II. Sumatra. Bull. Jard. Bot. Buitenzorg III, 14: 175-186.

Alston, A. H.G. 1939a. Notes on Selaginella: IX. Hie South African species. J. Bot. London 77: 221-224.

Alston, A. H. G. 1939b. The Selaginellae of Argentina, Uruguay and Paraguay. Physis (Buenos Aires) 15: 251-257.

Alston, A. H. G. 1940. The Selaginellae of the Malay Islands. III. Celebes and the Moluccas. Bull. Jard. Bot. Buitenzorg III, 16: 343-350.

Alston, A. H. G. 1945. An enumeration of the Indian species of Selaginella. Proc. Natl. Inst. Sci. India 11: 211-235.

Alston, A.H.G. 1951. Selaginellacées. In: Flore générale de l'lndo-Chine, vol.7. (H.Lecomte, Ed.) Paris: Masson & Cie. pp. 555-594.

Alston, A. H. G. 1952. A revision of the West Indian species of Selaginella. Bull. Brit. Mus. (Nat. Hist.) Bot. 1: 25-47.

Alston, A.H.G. 1955. The heterophyllous Selaginellae of continental North America. Bull. Brit. Mus. (Nat. Hist) Bot. 11: 219-274.

Alston, A.H.G. 1957. Selaginellaceae. In: Alston, A.H.G., Tardieu-Blot M. (Eds) Les ptéridophytes de l'Afrique intertropicale française. Mém. Inst. Fr. Afr. Noire 50: 26-44.

Alston, A. H. G. 1959. The ferns and fern allies of West Tropical Africa, being a supplement to the second edition of the flora of West Tropical Africa (R. W. Keay, Ed). London: Crown Agents.

Alston, A. H. G., Jermy, A. C., Rankin, J. M. 1981. The genus Selaginella in tropical South America. Bull. Brit. Mus. (Nat. Hist.) Bot. 9 (4): 233-330.

Baker, J. G. 1883. A synopsis of the genus Selaginella, pt. 1. J. Bot. London 21: 1-5.

Baker, J. G. 1887. Handbook of the fern-allies. London: Bell.

Bienfait, A., Waterkeyn, L. 1974. Contribution à l'étude systématique des Selaginella: spécificité des formations callo-siques foliaires observées en fluorescence. Bull. Jard. Bot. Nat. Belg. 44: 295-302.

Billington, C. 1952. Ferns of Michigan. Bull. Cranbrook Inst. Sci., 32:114.

Gulyas, S. 1961. Untersuchungen an der Blattepidermis der Selagineilen. Acta Biol. Univ. Szeged, N.S. 7:15-24.

Hellwig, R. L. 1969. Spores of the heterophyllous Selaginellae of Mexico and Central America. Ann. Missouri Bot. Gard. 56: 444-464.

Hieronymus, G. 1901. Selaginellaceae. In: Engler, A., Prantl, K. (Eds). Die natürlichen Pflanzenfamilien I, 4. Leipzig: Engelmann, pp. 621-715.

Homer, H. T., Arnott, H.J. 1963. Sporangial arrangement in North American species of Selaginella. Bot. Gaz. 124: 371-383.

Homer, H. T., Beltz, C. K. 1970. Cellular differentiation of he-terospory in Selaginella. Protoplasma 71: 335-341.

Homer, H. T., Beltz, C. K., Jaegels, R, Boudreau, R. E. 1975. Ligule development and fine structure in two heterophyllous species of Selaginella. Can. J. Bot. 53:127-143.

Jermy, A.C. 1970. Selaginellaceae. In: Schelpe, E.A.C.L.E. (Ed.) Flora Zambesiaca, Pteridophyta. London: Crown Agents, pp. 22-30.

Jermy, A. C. 1986. Two new Selaginella species from Gunung Mulu National Park, Sarawak. Kew Bull. 41: 547-559.

Jermy, A. C-, Jones, K., Colden, C. 1967. Cytomorphological variation in Selaginella. Bot. J. Linn. Soc. 60: 147-158.

Kempf, E. U. 1970. Elektronenmikroskopie der Sporodermis von Megasporen der Gattung Selaginella (Pteridophyta). Rev. Palaeobot. Palynologie 10: 99-116.

Knox, E. M. 1950. The spores of Lycopodium, Phyttoglossum, Selaginella and Isoetes and their value in the study of mi-

crofossils of Palaeozoic age. Trans. Bot. Soc. Edinburgh 35:209-357.

Kornas, J., Jankun, A. 1983. Annual habit and apomixis as drought adaptations in Selaginella tenerrima. Bothalia 14: 647-651.

Kunkel, G. 1963. Die Formvariabilitat einiger westafrikanischer Fame. Nova Hedw. 6:199-217.

Lee, D. W. 1977. On iridescent plants. Gard. Bull. Singapore 30: 21-29.

Leopold, A.C., Musgrave, M.E., Williams, K.M. 1981. Solute leakage resulting from leaf desiccation. Plant Physiol. 68: 1222-1225.

Loyal, D. S. 1976. Chromosome counts in north-western Himalayan species of Selaginella-1. Proa 63rd Indian Sri. Congr. PL 3: 127-128.

Lyon, F. M. 1902. Two megasporangia in Selaginella. Bot. Gaz. 36: 308.

Mickel, J.T., Hellwig, R.L 1969. Actino-plectostely, a complex new stelar pattern in Selaginella. Amer. Fern J. 59: 123-134.

Minaki, M. 1984. Microspore morphology and taxonomy of Selaginella (Selaginellaceae). Pollen Spores 26 (3-4): 421-480.

Mukheijee, R. N., Sen, U. 1981. A forked vein and foliar fibres in Selaginella. Fern Gaz. 12:175-177.

I*arris, B. S., Jenny, A. C, Camus, J. M, Paul, A. M. 1984. The Pteridophyta of Gunung Mulu National Park, Sarawak. In: Studies on the flora of Gunung Mulu National Park, Sarawak (A. C.Jermy, Ed.). Kuching: Forestry Department, pp. 145-233.

Pettitt, J. M. 1966. Exine structure in some fossil and recent spores and pollen as revealed by light and electron microscopy. Bull. Brit. Mus. (Nat. Hist.) Geol. 13: 223-257.

Pettitt, J. M. 1971. Developmental mechanisms in heterospo-ry. I. Megasporocyte degeneration in Selaginella. Bot. J. Linn. Soc. 64: (3): 237-246.

I'roctor, G. R. 1985. Ferns of Jamaica. A guide to the Pterido-phytes. London: British Museum (Natural Histoiy).

Quansah, N., Thomas, B. A. 1985. 'Sporophyll-pteryx' in African and American Selaginella. Fern Gaz. 13(1): 49-52.

Reed, C F. 1966. Index Selaginellarum. Mem. Soc. Brot. 18: 1-287.

Rothmaler, W. 1944. Pteridophyten-Studien I. Fedd. Rep. 54: 55-82.

Smith, A. R. 1981. Flora of Chiapas II. Pteridophytes. San Francisco: Cal. Acad. Sei.

Somers, P. 1982. A unique type of microsporangium in Selaginella, Series Articulatae. Amer. Fern J. 72: 88-92.

Spring, A. 1850. Monographie de la famille Lycopodiacees: 2. Selaginella. Mem. Acad. R. Sei. Lett. Belg. 24: 52-264.

Stolze, R. G. 1983. Ferns and fern-allies of Guatemala III. Field. Bot. N.S. 12:1-91.

Tagawa, M., Iwatsuki, K. 1979. Flora of Thailand 3 (1): Pteridophytes: 1-128.

Tryon, A. F. 1949. Spores of'the genus Selaginella in North America, north of Mexico. Ann. Missouri Bot. Gard. 36: 413-431.

Tryon, A. F., Lugardon, B. 1978. Wall structure and mineral content in Selaginella spores. Pollen Spores 20:315-340.

Tiyon, R. M. 1955. Selaginella mpestris and its allies. Ann. Missouri Bot. Gard. 42:1-99.

Wagner, W. H., Beitel, J. M., Wagner, F. S. 1982. Complex venation patterns in the leaves of Selaginella: megaphyll-like leaves of Lycophytes. Science 218: 793-794.

Walton, J., Alston, A.H.G. 1938. Lycopodiinae. In: Ver-doorn, F. (Ed.) Manual of pteridology. The Hague: Nij-hoff, Chap. 17.

Webster, T. R. 1967. Induction of Selaginella sporelings under greenhouse and field conditions. Amer. Fern J. 57: 161-166.

Wong, K.M. 1983. Critical observations on peninsular Malaysian Selaginella. Gard. Bull. Singapore 35:107-135.

Yasuo, S., Konishi, T., Kiyosawa, S. 1984. Studies on oligosaccharides of plants in the Selaginellaceae in Japan. Shoyakugaku Zasshi 38: 207-211.

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