146 Alexander W. Evans, 



chilensis in size, in color and perhaps in general habit, but the latter 

 species can be at once distinguished by its much more copious and 

 irregular branching and by differences in anatomical structure. 

 In the type material the plants are growing in mixed tufts with 

 other bryophytes and show a pale green color, becoming yellowish 

 with age. Here again it is difficult to determine the habit beyond 

 a doubt, but the thallus presents the appearance of being prostrate 

 or decumbent, with the apical portion perhaps ascending. The 

 rhizoids present are largely restricted to the stolons, which are not 

 very highly differentiated. 



The main axis (Fig. 4, D) continues its growth indefinitely and 

 terminates in a broad and truncate apical region ; in this respect it 

 differs from R. corralcnsis where the axis sometimes narrows to a 

 blunt point. The axis differs also in being wider, usually 0.8-1 

 mm. across instead of only 0.35-0.5 mm., but the length of the 

 living portion, 1.5-2 cm., is essentially the same. The thickness of 

 the axis is about 0.3 mm., indicating a considerable degree of flat- 

 tening. Each surface is somewhat convex, the ventral a trifle 

 more than the dorsal, and the latter sometimes shows a tendency 

 to be slightly concave in the outer part. From the median por- 

 tion, which is usually eight or nine cells thick, the thallus gradually 

 thins out to the margin, which appears blunt in cross section. In 

 the median portion the surface-cells measure about 40 fx in width 

 and 40-60 IX in length ; toward the margin a gradual increase in 

 width is shown, the marginal cells averaging about 50 x 50 /* and 

 forming an indistinct and often interrupted row. The interior 

 cells of the axis are mostly 120-160 /^ in length, but their diameter 

 is about the same as that of the surface-cells. The cross section, 

 therefore (Fig. 4, E, F), does not show an abrupt change in size 

 between the surface-cells and the interior cells, differing in this 

 respect not only from R. corralensis but also from R. spcctabilis 

 and R. Spegazziniana. The cell walls in R. cJiilcnsis are thin or 

 slightly and uniformly thickened ; sometimes the walls of the layer 

 just within the surface layer are a little thicker than the others, but 

 this difference is almost imperceptible. No pigmentation of the 

 walls has been observed. 



The primary branches arise close together, especially toward the 

 apex of the thallus. In many cases they are only i mm. apart on 

 each side and they may be even more crowded. They spread 



