LYCOPODIACE.E, 26 1 



the rest of the spore, originate the archegonia, corre- 

 sponding to those of Ferns and Horsetails. 



The upper and often greatly more numerous sporangia of 

 the fertile spikes contain only minute spores (microspores) 

 each of which may be regarded as the homologue of the 

 antheridium of a Fern with this difference, that a single 

 small cell of the microspore which takes no part in the 

 formation of anther ozoids has to serve as the representative 

 of a prothallium. Like the fern-antheridium the micro- 

 spore on its dehiscence liberates an indefinite number of 

 motile antherozoids, the confluence of which with the 

 protoplasmic contents of the germ-cell of an arche- 

 gonium determines the cell-division and growth which 

 result in the asexual generation of a new Club-moss. 



Here, therefore, as in Ferns and Horsetails, we have 

 the alternation of an asexual generation that is to say 

 the spore-bearing plant with a sexual one that is to 

 say the small prothallium developed from one kind of 

 spore in Lycopodium or the yet more rudimentary pro- 

 thallia shared between the microspores and macrospores 

 in Selaginella, upon which the antheridia and archegonia 

 respectively are borne. As in Ferns and Horsetails, too, 

 the asexual greatly dominates over the sexual generation. 



4. Natural Order Musci. The Moss Family. 



Type Hair-Moss (Polytrichuni). Any species will 

 serve. 



Minute leafy plants, with slender stems, bearing 

 sporanges upon erect, hair-like stalks (setce). They 

 usually grow socially in tufts, or when more widely 

 spread, in soft, carpet-like masses. 



The sporange is covered at first by a cap (calyptrd), 

 and is closed by a lid (ppercuium}, which separates when 

 ripe, exposing a row of minute teeth (forming the pert- 

 stome) around the margin of the sporange. 



The sporanges contain double-coated spores of one 

 kind, which, when they germinate, develop indirectly the 

 complete vegetative system that is, rootlets, branches, 

 and leaves of the Moss-plant. Indirectly, because in 

 Mosses proper, the spore on germination gives rise to a 

 delicate branching septate filament, upon which the leafy 

 shoots develop as lateral buds. Upon the leafy branches 



