8 Evans : Hepaticae of Puerto Rico 



RECTOLEJEUNEA 



The genus Rectolejeunea attains its highest development in the 

 tropical and subtropical regions of America. In fact it is doubtful 

 if it is represented elsewhere. In Puerto Rico four species have 

 been collected, none of them in abundance. All of these four 

 species occur on other West Indian islands, and two of them have 

 been found in southern Florida. All of the known species grow 

 on bark. The genus may be characterized as follows : — 



RECTOLEJEUNEA gen. nov. 



Lejeunea p. p. G. L. & N. Syn. Hep. 1845. 



Lejeunea subgenus Cheilo- Lejeunea p. p. Spruce, Hep. Amaz. et 



- And. 1884. 



Cheilolejeunea p. p. Schiffn. ; Engler & Prantl, Nat. Pflanzenfam. 



I 3 : 124. 1893. 



Plants small to medium-sized, sometimes delicate in texture, 

 sometimes firmer, pale- to deep-green, often becoming brownish 

 with age, not glossy : stems prostrate and adherent to the sub- 

 stratum, more or less branched, the branches prostrate or ascend- 

 ing : leaves loosely imbricated, the lobe widely spreading, some- 

 what falcate, ovate to orbicular in outline, plane or nearly so, 

 rounded at the apex or very obtuse, margin entire or sparingly 

 and minutely crenulate ; lobule inflated and forming a distinct 

 water-sac, keel straight or slightly arched, free margin involute 

 throughout a part of its length, tipped at the apex by a single 

 cell bearing a marginal hyaline papilla at its proximal base ; leaf- 

 cells plane or slightly convex, the walls sometimes thin with 

 more or less evident trigones, sometimes more uniformly thick- 

 ened ; ocelli frequently present : underleaves small, distant to sub- 

 imbricated, orbicular to ovate, bifid to the middle or beyond with 

 variable divisions and sinus : inflorescence autoicous or dioicous : 

 5 inflorescence sometimes borne on a short branch, sometimes on 

 a leading branch, simple or innovating on one side ; bracts obliquely 

 spreading, complicate, unequally bifid ; bracteole similar to the 

 underleaves but larger and usually less deeply bifid ; perianth 

 usually obovate in outline, compressed, the lateral keels prominent 

 and commonly sharp, antical face plane or nearly so, postical keel 

 low and broad, rounded or two-angled, apex truncate or slightly 

 retuse, with a short but distinct beak : <$ inflorescence occupying 

 short branches or intercalary on longer branches ; bracts imbri- 

 cated, diandrous (so far as known) : vegetative reproduction by 

 means of deciduous leaves. (Name from pnxric, fragile, and 



