66 



BOTANY AND PHARMACOGNOSY. 



LYCOPODIALES. 



The Lycopodiales, or Club Mosses (Fig. 46), are perennial 

 moss-like plants, with more or less erect or creeping and branching 

 stems, on which are borne numerous small simple leaves. The 

 sporangia arise either at the base of the upper surface of the leaves 

 or occur in terminal cones. They have short stalks, are uni- 

 locular and 2-valved. The asexual spores are of one kind in 

 Ly CO podium (Fig. 278b) and in the form of spherical tetrahed- 

 rons resulting from the manner in which division has taken place. 

 In Sclaginclla (Fig. 41) two kinds of asexual spores are produced, 



Fig. 42. Longitudinal section of young embryo of a Selaginella before separation 

 from the prothallus: et, suspensor; w, root; f, foot; bl, cotyledons; lig, ligules or bud 

 scales. After Pfeffer. 



that is, both microspores and megaspores, which in turn give rise 

 to male and female prothalli respectively. The microspore devel- 

 ops a male gametophyte (Fig. 43) which remains entirely within 

 the spore, and consists of a few-celled prothallus and a number of 

 mother cells which produce sperms that eventually escape by the 

 breaking of the wall. 



The megaspore frequently begins to develop the gameto- 

 phyte (Fig. 44) while still within the sporangium. The pro- 

 thallus consists of a number of cells and partly protrudes 

 through the ruptured spore wall. On the upper part of the pro- 



