

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. inundatum, L. salakcnse, 

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

 1 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 

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



I only modified. In L. annotinum, as described by Bruchmann, the 



I prothallium is subterranean and saprophytic, but still retains some 



I of the leafy appearance ; in L. later ale the crown is sometimes broken 



[ up into separate fleshy 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. annotinum, or some such species, germinate 

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



should appear. 



anatomy of the sporophyte 



structure of the adult sporophvte Lycopodi 



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. Treub (7), Bruchmann (13), Miss Wigglesworth i 



and Holloway (16) have figured and described a few section-; 

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



but 



little attention. 



portant feature 



