Evans: Notes on genus Herberta 197 



the same plane. At the base on each side a series of slime papillae 

 or their vestiges can be demonstrated. These are sometimes 

 sessile (Text fig. 17) and sometimes borne on the tips of more or 

 less evident teeth or cilia (Text fig. 7; Plate 8, fig. 5). Occa- 

 sionally slime papillae with their teeth are developed on the sur- 

 faces of the leaves and underleaves, as well as on their margins. 

 The teeth vary from short stalks a cell or two long to broad and 

 subdivided lobe-like structures. Except for the basal teeth as- 

 sociated with the slime papillae the margins are usually quite 

 entire. In a few species, however, distinct teeth are present 

 higher up, even beyond the region of the sinus, and these teeth 

 show no evidences of slime papillae. Even when teeth of this 

 character are present the upper parts of the divisions lack them 

 completely. A vague serrulation, caused by projecting cells, may 

 sometimes be discernible but seems to be a very exceptional 

 feature. 



Aside from the difference in insertion there are certain other 

 slight differences between the leaves and underleaves. The 

 leaves are usually curved backward and appear unsymmetrical 

 when dissected from the stems and spread out fiat. The curvature 

 affects the ventral division more strongly than the dorsal division 

 (Plate 8, figs. 1-3) ; the latter in fact may be straight or nearly 

 so while the ventral division is strongly curved (Text fig. i). 

 In some species the curvature is much less pronounced than in 

 others and may not be evident at all in explanate leaves (Text 

 figs. 22-25) ; the lack of symmetry, however, still expresses itself 

 in a difference of direction of the divisions and in a greater de- 

 velopment of the basal portion on the dorsal side. The under- 

 leaves bend backward in a squarrose fashion and appear symmet- 

 rical when spread out. their straight divisions diverging equally 

 and the basal portion being equally developed on the two sides. 

 The leaves and underleaves are usually more or less imbricated. 

 The divisions of the curved leaves and squarrose underleaves are 

 thus crowded together along the ventral portion of the shoot, the 

 plant acquiring a distinctly moss-like appearance. 



The cells and especially the cell-walls yield some of the most 

 distinctive characters of the genus. Most of the walls are strongly 

 thickened and this applies even to the rhizoids when they become 



