. Botany for high schools and colleges. Botany. SELAQINELLJE. 385 Four genera belong to tbis order, viz., Lycopodium, wliich is common in the wooded portions of tlie United States ; Psilotum, found in Florida; Tmesipteris and Phylloglossum, of Australia. Tbe species number from 115 to 130, of whicli about 100 belong to tbe genus. Tbe spores of Lycopodium clavatum are gathered in Europe and sold for various minor uses. Many species have a high ornamental value. This order was represented in tbe Devonian by species of Arctopo- dium. In the Carboniferous tbe genus I/yeopodium first appeared. The
. Botany for high schools and colleges. Botany. SELAQINELLJE. 385 Four genera belong to tbis order, viz., Lycopodium, wliich is common in the wooded portions of tlie United States ; Psilotum, found in Florida; Tmesipteris and Phylloglossum, of Australia. Tbe species number from 115 to 130, of whicli about 100 belong to tbe genus. Tbe spores of Lycopodium clavatum are gathered in Europe and sold for various minor uses. Many species have a high ornamental value. This order was represented in tbe Devonian by species of Arctopo- dium. In the Carboniferous tbe genus I/yeopodium first appeared. The closely related extinct order Lepidodendrese first appeared in the Devonian, in which it was represented by two known species of Lepi- dodendron ; in tbe Carboniferous this genus was represented by sixty or more species, many of gi- gantic size, and the order by many other generaâ, Le-pidophloios, Lepidostro- bus, Halonia, etc. In the Permian tliis order became extinct. Another orderâtbe Sigil- larjeaeâwas represented by many species of Sigillaria in the Carboniferous period. Like the preceding, this or- der became extinct in the Permian. Order Selaginellce.â Tbe prothallia aredioecious. Those which develop from the macrospores consist of a spore. /. X 5; II. x 3; â ^ ,, , meiBter. concavo-convex many-celled. structure, which develops upon, and has its concave side applied to, tbe convex surface of tbe spore. Upon its convex surface, which protrudes through the ruptured wall of the spore, are a few root-hairs and many deeply sunken arcliegonia (Fig 276,1, 3, 3). The microspores develop only tbe smallest rudiments of prothallia. In germination a single cell (», Fig. 376, D) is first of all cut off ; this undergoes no further change, and is doubtless to be regarded as the prothallium. The re- mainder of the spore becomes divided in a regular way into a few large primordial cells (Fig. 376, A), and from these great numbers of sperm-cells are produced (Fig. 376, D). Aft
Size: 2021px × 1236px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1888
