226 



cated, the lobe widely spreading but scarcely falcate, ovate-oblong 

 to subrotund, more or less convex and often revolute at the 

 rounded to very obtuse apex and along the postical side, margin 

 entire or subdenticulate from projecting cells ; lobule inflated 

 throughout, the free margin more or less strongly involute to or 

 beyond the apex, the opening into the water-sac bemg largely 

 formed by the sinus, apical tooth varying from blunt to long- 

 acuminate, hyaline papilla marginal, borne at the distal base of 

 the apical tooth and more or less displaced from the terminal 

 cell ; leaf-cells plane or convex, thin-walled or with the free outer 

 walls a little thickened, trigones small, mostly triangular with 

 concave sides, intermediate thickenings occasional or rare ; ocelli 

 none : underleaves distant to imbricated, orbicular to reniform, 

 entire, broad and undivided at the rounded apex, abruptly narrowed 

 to subcordate at the base : inflorescence mostly autoicous : 2 

 inflorescence sometimes borne on a short branch, sometimes on a 

 leading branch, innovating on one side or occasional 1}^ on both, the 

 innovations mostly short and sterile but sometimes again florifer- 

 ous ; bractssimilar to the leaves, unequally bifid and complicate, the 

 keel mostly rounded but sometimes narrowly winged ; bracteole 

 free, rounded to slightly retuse at the apex, obovate ; perianth 

 obovoid, scarcely compressed, rounded to subretuse at the apex 

 with a distinct beak, five-keeled, antical keel low and sometimes 

 indistinct, lateral keels sharp, postical keels rounded to sharp, keels 

 smooth or minutely and irregularly crenulate or denticulate from 

 projecting cells, rarely obscurely winged : c^ inflorescence occu- 

 pying a short branch ; bracts mostly two to six pairs, imbricated, 

 strongly inflated, slightly and subequally bifid with rounded 

 lobes and a strongly arched keel, diandrous ; bracteoles similar 

 to the underleaves but smaller, limited to the base of the spike. 

 (Name from h'jxb:;, white, and Lcjciinea, in allusion to the pale 

 color of the plants.) 



In distinguishing Archilcjcunea and Lc7icolcjcu)ica from each 

 other the most important of the differential characters are those 

 derived from the vegetative organs and the antheridial spikes. 

 The species of Arcliilejeunca, for example, show a marked dis- 

 tinction between a creeping caudex and secondary stems, whereas 

 xrv Leiicolejennea no such distinction is apparent. In Archilejeunea 

 the plants are more or less pigmented, the hyaline papilla of the 

 lobule is borne at the proximal base of the apical tooth, the 

 trigones of the leaf-cells are large and conspicuous, the inter- 

 mediate thickenings are scattered throughout the lobe, and the 



