American Species of Marchantia. 



245 



sexual receptacles are larger than in the most robust forms of 

 M. polynwrpha, approaching or equalling in this respect the 

 more southern M. Bcrtcroana. The thallus also shows a tendency 

 to fork at infrequent intervals, so that it presents the appearance 

 of being more elongated than in M. polymorpha. 



The lack of epidermal papillae on the rays of the female 

 receptacle seems also to be a distinguishing character. In fact 



Fig. 4. Marchantia plicata Nees & Mont. 



Anatomical details. A-C. Epidermal pores of thallus, surface view, 

 X 225. D. Pore in cross-section, x 225. E. Inner opening of pore, x 225. 

 F, G. Two parts of the same involucre. A, B, D, E. Peru, Cook & 

 Gilbert 1162, 1321. C. Bolivia, A. d'Orbigny, type. F, G. Colombia, 

 W. Weir. 



papillae of tliis type are restricted to the outer surface of the 

 cupules. In spite of the large size of the thallus the epidermis of 

 M. plicata is unusually delicate in texture and the air-chambers 

 unusually low. 



The ventral scales exhibit considerable variation witli respect 

 to size and amount of pigmentation. In typical examples the 

 ventral surface is almost covered with purple scales, but this con- 

 dition is by no means constant; the scales may only partially 

 cover over the surface and the pigmentation may be very slight. 



