Discoid gemmae ir, the leafy hepatics of New England 
NEIL E. STEVENS 
The gemmae found among the leafy Jungermanniales belong, 
with very few exceptions, to two distinct types. Those of the 
simpler type are unicellular or bicellular bodies which arise, 
generally in clusters, from the leaves or from the stem in the region 
of the apex. Those of the second type are discoid, multicellular 
bodies which are borne either on the margins or the surfaces of the 
leaves. The formation of the simpler type of gemma seems often 
to be associated with limitation of growth, for when the gemmae 
are borne on the stem the entire growing point goes over to the 
production of gemmae. The production of discoid gemmae, how- 
ever, rarely seems to affect the growth of the plant toany marked 
degree. Gemmae of the simple type are of much more frequent 
occurrence, especially among northern forms, and are found in the 
vast majority of the gemmiparous New England species. Discoid 
gemmae occur, on the other hand, chiefly among the tropical epi- 
phyllous forms. In New England they are known in only two 
species, Cololejeunea Biddlecomiae (Aust.) Evans and Radula com- 
planata (L.) Dumort. According to Nees von Esenbeck discoid 
gemmae occur also on Lejeunea cavifolia (Ehrh.) Lindb. (L. ser- 
pyllifolia Lib.), but as he describes them, they represent here actual 
pieces of the leaf which become separated and are therefore hardly 
to be considered differentiated gemmae. 
In the present paper the development and structure of the 
gemmae of Cololejeunea Biddlecomiae and Radula complanata are 
discussed. Both of these species are widely distributed in North 
America, and Radula complanata occurs also in Europe, Asia, and 
northern Africa. The material used in the study of Cololejeunea 
Biddlecomiae was collected by the writer in Woodbridge, Con- 
necticut, in March. Material from Superior, Wisconsin, collected 
in August by G. H. Conklin, was used for comparison. The 
material of Radula complanata was collected in North Haven, 
Conn., in October, specimens collected at Woodbridge, Conn., 
365 
