289 
Evans .— Vegetative Reproduction in Metzgeria. 
below was collected on Mount Morales, near Utuado, Porto Rico, on 
March 15, 1906, by E. G. Britton and D. W. Marble (No. 498). Its 
determination as M. dichotoma must be considered somewhat doubtful, 
since the Jamaican specimens examined by the writer are entirely destitute 
of gemmae. Lindberg, however, notes the occurrence of surface gemmae 
in this species although he fails to mention any of their peculiarities. The 
gemmiparous branches in the Porto Rican plants are scarcely if at all 
modified, and there seems to be no marked tendency for their growth to be 
limited. The gemmae arise in considerable abundance, but without definite 
order. An alar cell which is to give rise to a gemma first bulges in the 
Fig. 13. M. dichotoma. A. A gemma at time of separation, x 80. b. A germinating 
gemma showing the two young thalli. x 80. 
usual way and then divides by a longitudinal wall before forming the 
transverse wall which marks off the future gemma. The result is that the 
gemma leaves behind two small thallus cells when it becomes separated. 
The gemmae are very remarkable from the fact that each of the two cells, 
of which the young rudiment consists, develops regularly an apical cell 
after a few divisions, and the two apical cells persist and continue their 
activities until the gemma is ready to separate. The gemma is accordingly 
symmetrically developed, and the condition which is found in M. crassipilis 
as a rare exception is here the rule. A mature gemma (Fig. 13, a) is 
a circular or reniform plate of cells, perfectly plane and showing no 
u 
