132 



SELAGINELLACE/E. 



and rough walls of the spore split apart at the apex, 

 exposing the part of the prothallium bearing the arche- 

 gonia, and these, after fertilization, contain the develop- 

 ing plants. On account of the early development of the 

 prothallium, and various other features connected with 

 the manner of spore production, the selagi- 

 nellas are thought by many students to be more 

 nearly related to the flowering - plants than 

 are any other Pteridophytes. The fertile spikes 

 differ very little from the flowers of the pines 

 and their allies. The most noticeable distinc- 

 tion is that the microspores of the pines (called 

 pollen) are borne in separate catkins. 



In most other respects the selaginellas have a 

 general resemblance to the lycopodiums, but 

 except in tropical countries this is is not close 

 enough to be confusing. Our North American 

 species are easily distinguished by their much 

 smaller size ; in fact they are so diminutive 

 that they are much likelier to be confused with the 

 mosses than with the lycopodiums. 



In our species the main stems seldom reach a length of 

 more than six inches. Often they are trailing, but occa- 

 sionally they are more erect. The trailing species, as in 

 the lycopodiums, send out forking roots at frequent 

 intervals, but the species with upright stems root only 

 near the base. The stems are usually branched, though 

 not dichotomously so, and the whole plant is generally 

 very close to the earth. 



The leaves are minute and very abundant, clothing 

 both stems and branches. The form of the leaves has 

 been made the basis for dividing the genus into two 

 sections. In one they are all alike and arranged in man}^ 



Spike of 

 Selaginella. 



