1917] CHAMBERLAIN— LYCOPODIUM 61 



Origin of the subterranean habit. — That the green leafy 

 prothallia represent the original type from which the subterranean 

 forms have diverged can scarcely be doubted. The species with 

 green, leafy prothallia (L. cernuum, L. inundation, L. salakense, 

 and L. latcrale) have spores which, in the first 3 species, are known 

 to germinate immediately; while in all those with subterranean 

 prothallia the spores germinate only after a long resting period. 

 It would seem that some change has occurred in the spore which 

 has delayed the germination; and then only such spores as reached 

 a protected situation would survive to germinate at all. Germinat- 

 ing in protected situations, with little or no light, the prothallia 

 naturally would assume the forms of subterranean, dependent 

 structures. That this has been the order of regression is indicated 

 by the fact that the leafy crown has not been lost altogether, but 

 only modified. In L. annolinum, as described by Bruchmann, the 

 prothallium is subterranean and saprophytic, but still retains some 

 of the leafy appearance ; in L. laterale the crown is sometimes broken 

 up into separate flesh} - cushions which may represent leafy lobes; in 

 more extreme cases, there is merely a swollen, fleshy rim to repre- 

 sent the leafy structure. The position of antheridia and archegonia 

 is about the same as in the green, leafy forms. 



If those who are expert in hastening the germination of seeds 

 which normally have a long resting period, could find some way to 

 make the spores of L. annotiimm, or some such species, germinate 

 immediately, it would not be surprising if green, leafy prothallia 

 should appear. 



ANATOMY OF THE SPOROPHYTE 



In the vascular structure of the adult sporophyte Lycopodium 

 still presents some difficult problems, although investigations like 

 those of Hill and others have cleared up some of the phases. How- 

 ever, it seems likely that the final solution will come through a 

 comparative study of sporelings, intermediate stages, and adult 

 plants. Tretjb (7), Bruchmann (13), Miss Wigglesworth (14), 

 and Hollo way (16) have figured and described a few sections; but 

 material has been scanty or other features of the problem have so 

 engrossed the attention that this important feature has received 

 little attention. 



