68 



BOTANY AND PHARMACOGNOSY. 



gametophytes consist of but a few cells. While the group is het- 

 erosporous and the gametophytes resemble those in Selaginella, 

 the sperms are multiciliate and coiled as in the Ferns. 



Distribution and Uses of Lycopodiales. — A number of the 

 Lycopodiums are common on rocks, damp woods, sandy bogs, 

 and illustrations of several of these are shown in Fig. 46. Some 

 tropical species are used in medicine ; the spores particularly of 

 Lycopodium clavatum (Fig. 46, illus. 3) are used as a dusting 

 powder (Fig. 278b), and for burning in the production of flash 



Fig. 44. The female gametophyte of a Selaginella; prothallus (pr) projecting through 

 the ruptured wall (spm) of the megaspore; ar, sterile archegonium; emb^, emb^, two 

 embryos embedded in the tissue of the prothallus; et, et, suspensors. — After PfefEer. 



lights. The Selaginellas (Fig. 45, A), of which there are several 

 species, are commonly used for decorative purposes. Some species 

 are, however, also used in medicine, and it is interesting to note 

 that the spores of one species {Selaginella selaginoides) are used 

 like those of Lycopodium. 



While the Pteridophytes do not form a very conspicuous por- 

 tion of the flora at the present time and yield but few products 

 of use to man, it may be pointed out that in former ages they 

 formed the dominant vegetation of the earth. Many of the 

 ancestral forms of this group attained the size of trees and made 

 up the forest vegetation during the Devonian and Carboniferous 

 Ages, the latter being sometimes spoken of as the age of Pterido- 



