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PHARMACEUTICAL BOTANY 
SUBDIVISION I.—LYCOPODINE^E OR CLUB MOSSES 
Small perennial, vascular, dichotomously branched herbs with 
stems thickly covered with awl-shaped leaves. The earliest forms of 
vascular plants differing from ferns in being comparatively simple in 
structure, of small size, leaves sesssile and usually possessing a single 
vein. Except in a few instances the sporangia are borne on leaves, 
crowded together and forming cones or spikes at the ends of the 
branches—Homosporous. 
Fig. 156. —Lycopodium clavatum. (Gager.) 
Family I.—Lycopodiaceae, including the single genus Lycopodium 
wi th widely distributed species. The spores of Lycopodium clavatum 
are official. 
Family II.—Selaginellaceae, including the single genus Selaginella 
with species for the greater part tropical. Plants similar in habit to 
the Lycopodiaceae but showing heterospory. 
Family III. -Isoetaceae, including the single genus Isoetes whose 
species are plants with short and tuberous stems giving rise to a tuft 
