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 flat. The curvature 
affects the ventral division more strongly than the dorsal division 
(PLATE 8, FIGS. I-3); the latter in fact may be straight or nearly 
so while the ventral division is strongly curved (TEXT FIG. 1). 
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 imbricat 
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 
