314 EVANS. 



Hairs vary somewhat in abundance and are apparently restricted to 

 the margin, the ventral surface being entirely naked throughout. In 

 many cases the margin is likewise hairless for long stretches, but at 

 the other extreme the hairs may occur between every two marginal 

 cells. They usually extend in the same direction as the wings, rarely 

 being numerous enough to form a weft in the space between the 

 margins. According to the original description the hairs often occur 

 in pairs or even in three's. The writer, however, has been unable to 

 verify this statement. So far as his observations go the hairs are 

 invariably borne singly, arising in the usual way from small cells cut 

 off from the marginal cells. In rare instances the marginal cells 

 themselves may project directly as hairs, especially if a rhizoidal 

 function is assumed, and under these circumstances two hairs may be 

 situated side by side, but this is very different from the usual paired 

 condition. Sometimes the hairs are short and spine-like with strongly 

 thickened walls, yet this type of hair is exceptional, most of them 

 being of the usual slender type and measuring 0.09-0.15 mm. in length 

 by about 10 fx in width. They are truly marginal in position. 



The costa, as described by Schiffner, is uniform in structure, being 

 bounded both dorsally and ventrally by two rows of cortical cells. 

 The alar cells are unusually small, averaging about 28 X 24 ju, although 

 somewhat larger cells are often interspersed among the others. The 

 walls are distinctly thickened and show indistinct trigones and occa- 

 sional intermediate thickenings. 



The male plants bear sexual branches in some abundance. The 

 latter are oval to globular in form, measuring usually 0.3-0.35 mm. in 

 length by 0.25-0.35 mm. in width and their cells are but slightly 

 smaller than those of the vegetative thallus. Although the costa is 

 strongly incurved the apex of the branch does not usually approach 

 the base very closely. No appendicular organs are present except the 

 slime-papillae. 



The female branches are broadly obovate and deeply indented at the 

 apex. They are mostly 0.3-0.35 mm. long by 0.45-0.6 mm. wide, and 

 their concave halves approach each other so closely before fertilization 

 that their margins are almost in contact. Ventral hairs are usually 

 completely absent, but in two instances a single such hair was seen 

 growing out from the thickened median portion. Marginal hairs, on 

 the contrary, are fairly abundant, and represent outgrowths of small 

 cells, just as in a normal vegetative thallus. They are mostly short 

 and spine-like, with strongly thickened walls. The calyptras at 

 maturity are mostly 1.5-2.5 mm. long and 0.7-0.85 mm. in diameter. 



