Evans : Hepaticae of Puerto Rico 9 



Lejeiinea, in allusion to the fact that the leaves in most of the 

 species easily become broken off.) 



In distinguishing Rectolejeimea from the genera to which it is 

 closely allied, the most trustworthy characters are those derived 

 from the lobule and from the perianth. The latter organ is essen- 

 tially the same as in Cheilolejeunea, but the lobule, as has already 

 been pointed out, is built up on an entirely different plan. In the 

 structure of the lobule, however, Rectolejeimea agrees pretty closely 



with Pycnolejeunea and Lejeiinea, and it is here that the flattened 

 perianth with its plane antical face serves as a distinguishing mark. 



So far as the structure of the leaves and underleaves is concerned, 



the new genus is in many respects intermediate between Pycnole- 



jeunea and Lejcnnea. It would even be possible, if the perianths 



were left out of consideration, to divide the species of Rectolejeimea 



between these two genera, without violating to any great extent 



their natural relationships. 



I 



Of the four species noted below two have recently been 

 described by the writer in another connection. It has therefore 

 seemed unnecessary to redescribe them in full. The first species 

 may be considered the type of the genus. 



Rectolejeunea flagelliformis sp. nov. 



Pale-green, becoming brownish with age, scattered or growing 

 in depressed mats : stems 0.09 mm. in diameter, closely adherens 

 to the substratum, sparingly and irregularly pinnate, the branchet 

 widely spreading, not microphyllous ; rhizoids numerous : leaves 

 imbricated, the lobe plane and appressed to the substratum, slightly 

 falcate, ovate, 0.7 mm. long, 0.4 mm. wide, antical margin rounded 

 at the base, arching partially or wholly across the axis and out- 

 wardly curved to the apex, postical margin straight or nearly so, 

 apex broad and rounded, margin entire or minutely and irregularly 

 crenulate from projecting cells ; lobule inflated, ovate in outline, 

 0.17 mm. long, 0.12 mm. wide, keel slightly arched, forming an 

 almost continuous line with the postical margin of lobe but usu- 

 ally with a notch at the junction, free margin curved, involute at 

 the base but appressed to the lobe throughout the greater part of 

 its length, apical tooth long and sharply curved, papilla in a dis- 

 tinct depression, sinus lunulate ; cells of lobe plane or slightly 

 convex, averaging 9 fi at the margin, 14 fi in the middle and 

 18 x 16 jx at the base, rather thick-walled but without distinct 

 trigones • ocelli mostlv three to six. arranged in one or two short 



