4 Evans : Hepaticae of Puerto Rico 



because, instead of projecting beyond the free margin of the lob- 

 ule, it bends sharply backward from its base and lies closely ap- 

 pressed to the inner surface. This position is assumed in very 

 immature leaves and is maintained as long as the papilla persists. 



The lobular differences just described are accompanied by 

 other differences of greater or less importance. In the opinion of 

 the writer they form a convenient basis for the segregation of the 

 old genus Cheilolcjennea into three genera. The first of these, for 

 which the name Chcilolejeiinea may be retained, is made up of spe- 

 cies showing the first type of lobule. For species showing the 

 second type, the name Rectolejeunea is suggested. C. lineata, 

 finally, which exhibits the third type of lobule, seems sufficiently 

 distinct to represent the new genus Cystolejeunea. Unfortunately 

 the structure of the lobule has not been carefully described for all 

 of the species which have been referred to Cheilolejeiinea, and cer- 

 tain of these cannot be definitely assigned at the present time. It 

 is even probable that some of them will fit more naturally into 

 Euosmolejeiinea or Pycnolejeunea than into any one of the proposed 

 generic segregates. 



In its restricted sense the genus Cheilolejeuriea is best developed 

 in the tropical and subtropical regions of America. So far as we 

 know at present the species are all found on bark, where they 

 sometimes form pure mats and sometimes grow mixed with other 

 hepatics of similar habit. The only species known from Puerto 

 Rico is C. decidna (Spruce) Evans. 



The plants belonging to this genus are pale- or bright-green in 

 color and are never glossy ; upon drying they sometimes become 

 brownish. The stems are prostrate and loosely adherent to the 

 substratum, the rhizoids being sparingly developed. The lobes of 

 the leaves are plane or slightly convex and are also appressed to 

 the substratum (plate I, figure i); they are falcate and vary in 

 shape from ovate to orbicular ; the apex is broad and usually 

 rounded, and the margin, which is entire or nearly so, is also 

 rounded but never distinctly cordate at the antical base. The 

 leaf-cells are plane or slightly convex, with firm walls ; trigones 

 are distinct and often conspicuous, and intermediate thickenings 

 occasionally occur (figure 2). Ocelli are not developed. The 

 underleaves are distant and small, being scarcely twice the width 



