GAMETOPHYTE AND YOUNG SPOROPHYTE OF LYCOPODIUM CAROLINIANUM

Gametophytes of Lycopodium carolinianum L. are green and superficial. Rhizoids invest the lower surface of the dorsiventral axes, multicellular lobes, the upper surface. Growth is apical. Gametangia occur mixed and always between lobes or around the lobe bases. Embryogeny is abbreviated with no protocorm. Following protophyll emergence, the rhizome apex forms laterally and the first root is initiated. Development of dorsal leaves, characteristic of adult rhizomes, is delayed until after the second pair of lateral leaves has formed. Features of the gametophyte and embryonic stages of the sporophyte provide additional comparative evidence supporting the view that L. carolinianum arose from along the phylogenetic line leading from subgenus Lepidotis to subgenus Lycopodium. GAMETOPHYTES and young sporophytes of Lycopodium are poorly known. Gametophytes of only 28 species have been described in a genus of over 400 species (Bruce, 1979). Embryogenesis is even less well known. Virtually all descriptions in modern morphology texts are derived from studies of two species (L. clavatum, Bruchmann, 1898; and L. cernuum, Treub, 1884, 1890). In fact, Bierhorst (1971, p. 22) states: "The embryogeny of Lycopodium is not known with the degree of certainty implied in many general accounts. None of the information on embryogeny has been documented with photographs. For the most part the descriptions are based on a limited and insufficient quantity of material, and there have been no confirmative studies." In this paper mature gametophytes and juvenile sporophytes of Lycopodium carolinianum L. are described. The development and maturation of the gametangia are photographically documented and all but the earliest stages of sporophytic development are described and illustrated. The patterns of growth and morphology of the gametophytes and young sporophytes 1 Received for publication 11 January 1979; revision accepted 28 June 1979. I thank John D. Gilman for his assistance in collecting these gametophytes. This work was supported in part by National Science Foundation Grant No. DEB-7902926. is compared with similar structures and stages of other species in assessing the phylogenetic placement of this taxon. MATERIALS AND METHODs-All gametophytes and young sporophytes were collected in early January, 1976 (Bruce 76002). The site was the sandy edge of a roadside borrow pit in the coastal plain of North Carolina. Prior to preservation of gametophytes in CRAF IV (Sass, 1958), color photographs were made of some specimens. Subsequently additional photographs of whole gametophytes and attached sporophytes were made on Kodak Panatomic-X film. A total of 16 gametophytes were studied. Eight of these were embedded and sectioned at 10 gm by using standard paraffin techniques (Johansen, 1940) and were stained after Sharman's (1943) schedule. Kokak SO-115 film was used for the photographs of sectioned materials. RESULTs-General description-The gametophytes of L. carolinianum are superficial and bright green. The specimens herein examined range in size up to 2.7 mm with the plants consisting of two parts, an elongate, tapering, basal portion and a larger parenchymatous main body bearing the gametangia (Fig. 1-6). The gametophytes are axial and dorsiventral, and they grow from a laterally disposed apical meristem. Fig. 1-16. Gametophytes of Lycopodium carolinianum.-Fig. 1-6. Whole gametophytes. 1. x25. 2. x25. 3. x40. 4. x 25. 5. x 25. 6. x 25. 7. Cross section of tapering base. Intercellular mycorrhizal fungi in epidermis, intracellular mycorrhizal fungi in central portion. x 210. 8. Section of main body, darker globules are mostly starch. x 240. 9. Rhizoid with intercellular hypha. Strutlike bars and projections also apparent. x650. 10. Tiered cell layers in main body. x350. 11. Endophytic fungal regions in main body. Intercellular fungi in epidermis and adjacent cell layer, intracellular fungi in subjacent region. x215. 12. Rhizoid base and subjacent cells with intercellular fungi, lower cell with distinct fungal coil. x550. 13. Section through meristem, in horizontal plane. x225. 14. Cross of gametophyte in Fig. 4, 5. x65. 15. Section through meristem, vertical plane parallel to gametophyte axis. Developing lobe just above meristem. x225. 16. Developing lobe. x 120. M, meristem.