438 PTERIDOPHYTES (FERN PLANTS) 



tively. The gametophytes are small, green, ribbon-like bodies and 

 lie flat on the surface of the substratum. The male gametophyte 

 is the smaller and is one cell in thickness. It bears the antheridia 

 on the tips of the lobes or on the margin. The female gametophyte 



Fig. 391. — The gametophytes of Equisetum arvense. A, female gameto- 

 phyte, showing one archegonium {ar) (X about 20). B, male gametophyte 

 with four antheridia showTi {$) {X about 40). 



forms a cushion, a number of cells in thickness, on the upper sur- 

 face of which the archegonia are borne. 



The multiciliate sperms, after being set free from neighboring 

 male gametophytes, swim to the archegonia and down their necks 

 to the eggs. The fertihzed egg begins to develop immediately 

 and continues until a new sporophyte is formed, and the hfe cycle 

 is thus completed. 



Lycopodiales (Club Mosses) 



About one-eighth of the hving Pteridophytes are Club Mosses. 

 They are commonly divided into four groups — Lycopodium 

 Phylloglossum, Selaginella, and Isoetes — but a study of the 

 Lycopodiums and the Selaginellas will serve to give a general 

 notion of the Club Mosses. 



The Club Mosses, although not IMosses at all, get their name 

 from their Moss-like stem and their club-shaped appearance due 

 to the large terminal strobili which some have. 



Lycopodium. — There are several hundred species of Lycopo- 

 diums, and they are widely distributed, occurring in both hemi- 

 spheres and from the torrid to the frigid zones. They prefer 

 shady places and some are aquatic. 



