CLUB-MOSSES 161 



a female prothallus of E. maximum, enlarged about 

 30 diameters, indicating the position of the archegonia. 

 The female prothalli are usually larger than the male. 

 The antheridia are very simple, and the spermatozoids 

 are very similar to those of Ferns (p. 150). Fertilization 

 can take place only in the presence of water. The 

 sporophyte i.e., the Horsetail " plant," soon becomes 

 independent of the prothallus. 



The Horsetails are a very distinct family; they are 

 not likely to be confused with the Ferns, yet there is a 

 striking resemblance between the reproductive organs, 

 and especially the spermatozoids, of the two families. 

 On account of this resemblance it is suggested that both 

 Ferns and Horsetails had a common origin, from which 

 the two became more and more divergent in their 

 evolution. 



LYCOPODIALES : CLUB-MOSSES. 



The Club-Mosses, by reference to which we conclude 

 our outline of the Pteridophytes, are not Mosses in the 

 strict sense of the term; it is only deference to popular 

 usage that permits the retention of their misnomer. 

 By way of general definition, we may say that the 

 Lycopodiales are plants that usually have long branching 

 stems, bearing relatively small leaves; they produce 

 spores, not seeds, and the spores are developed in 

 sporangia borne in the leaf axils, or on the upper surfaces 

 of the fertile leaves, which in numerous instances occur 

 in aggregations of the nature of cones. There are homo- 

 sporous and heterosporous (p. 144) families. Of course, 

 there is the usual alternation of generations. Another 

 feature consistent throughout the group is the production 



21 



