The structure & development of the mosses and ferns (Archegoniatae) . es, and a few species of Selaginella, , have a wider range ; but the great majority of thespecies are found only in the moist forests of the tropics. Thegametophyte of the homosporous forms is known only in Lyco-podium, and this only within a comparatively short time. Ourknowledge of it is based mainly upon the important researchesof Treub, but these have been added to by Goebel ^ in the caseof L. inundatmn. The gametophyte in its earliest condition, sofar as is certainly known, develops chlorophyll, and this
The structure & development of the mosses and ferns (Archegoniatae) . es, and a few species of Selaginella, , have a wider range ; but the great majority of thespecies are found only in the moist forests of the tropics. Thegametophyte of the homosporous forms is known only in Lyco-podium, and this only within a comparatively short time. Ourknowledge of it is based mainly upon the important researchesof Treub, but these have been added to by Goebel ^ in the caseof L. inundatmn. The gametophyte in its earliest condition, sofar as is certainly known, develops chlorophyll, and this con-dition may be permanent, L. cernuuin, but other forms havea chlorophylless prothallium, and are saprophytic in habit, likeOphioglossum. The germination of these forms is at presentunknown. The sporophyte has the axis strongly developed, and theleaves, though usually numerous, are simple in structure andgenerally small. The genera are all homosporous exceptSelaginella, which is very markedly heterosporous, and has the 1 Baker (2). Treub (2). 3 Goebel (18).. Fig. 243.—Part of a fruiting plant of Lycopodiuvi cla-jatum (L.), X |; B, sporophyll, with sporangium{sp) of L. dcndroideuml(l>>lichx.), x 12 ;.C, cross-section near the base of an aerial shoot of , X12. CHAP. XIV LYCOPODINEAL 463 gametophyte very much reduced and projecting Inil little beyondthe spore wall. Classification A. HomosporecB I. Roots always present ; sporangia alike, simple, in theaxils of more or less modified leaves, which may form a distinctstrobilus, or may be but Httle different from the ordinary onesboth in form and position ; prothallia either green or colourless,monoecious. Order I. Lycopodiace^ Genera 2.—(i) Lycopodium ; (2) PJiylloglossum II. Roots absent; vegetative leaves much reduced (^Psi-lotuni) or well developed ; sporophylls petiolate, bilobed ; spor-angia plurilocular ; gametophyte unknown. Order II. 2.—(i) Psilotuni ; (2) Traesipteris B. He
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