236 



Alexander W. Evans, 



terized by a lax habit and by female receptacles having elongated 

 rays and long slender stalks; B. alpestris, by a compact habit 

 and by female receptacles having shorter rays and shorter and 

 thicker stalks. 



Nees von Esenbeck's varieties and subordinate groups are 

 accepted without question in the Synopsis Hepaticarum, but later 



Fig. I. Marchantia polymorph a L. 



Appendages of ventral scales, x 100; F represents the basal portion of 

 an appendage ; the other figures represent apical portions. A. Opdal, 

 Norway, /. Hagen, in V. Schiflfner's Hep. Europ. Exsic. 15, type of var. 

 mamillata Hagen. B-D. New Haven, Connecticut, A. W. Evans. E, F. 

 Wilbraham, Massachusetts, E. A. Chapin, forma aquatica. G. Mount 

 Hood, Oregon, /. Roll, type of M. oregonensis Steph. H. Oaxaca, E. W. 

 Nelson 2530. I. Jamaica, A. W. Evans 176. J. Patagonia, /. B. Hatcher. 



writers have largely neglected them. There are two, however, 

 which appear from time to time in local lists and taxonomic 

 works. One of these is A. communis, a aquatica, usually quoted 

 as "var. aquatica Nees/' and the other is B. alpestris, quoted 

 as "var. alpestris Nees." The differences between these two 

 so-called varieties are indeed striking. In var. aquatica the 

 thallus shows a distinct median band on the upper surface usually 

 pigmented with purple and associated with the absence of air- 



