1 88 Alexander W. Evans, 



1-1.5 mm. long and 0.2-0.3 mm. wide. They are sometimes simple 

 and sometimes give rise to one or two shorter and narrower second- 

 ary branches. The tips of the obliquely spreading branches and 

 their subdivisions are decurved and not infrequently grow out into 

 subterete extensions or stolons. They thus form a sort of con- 

 necting link between the typical obliquely spreading branches and 

 the true stolons, which grow backwards almost from the beginning. 

 These stolons, although limited in growth, are sometimes longer 

 than the branches just described and may be simple or sparingly 

 branched. In their histological features the branches with limited 

 growth are much like the axis, except that the walls are pretty uni- 

 formly thin. There is also, especially in the stolons, less difference 

 in size between the superficial and interior cells, the latter averaging 

 only 25 /A in width. A typical stolon is about fifteen cells wide and 

 twelve thick. 



No male plants have been seen by the writer, but Stephani gives 

 a full description of the male branches. These are as wide as the 

 axis and are borne singly, sometimes on the axis itself, sometimes 

 on a flattened branch, sometimes on a stolon, and a regularly pin- 

 nate arrangement may be present. The inflorescence is deeply 

 bilobed at the apex, canaliculate above, and bordered by erect, 

 foliaceous, papulose-crenate wings. The antheridia number ten 

 or less. The female branches studied by the writer are very short 

 and arise directly from the axis or a leading branch (Fig. 12, 

 E, H). The wings are mostly eight or ten cells wide and deeply 

 divided into a few irregular lobes, which are mostly blunt and 

 vaguely crenulate from projecting cells. The archegonia are 

 directed forward and no more than four have been observed in 

 any inflorescence. The "calyptra", according to Stephani, is 

 cylindrical, papulose, and tipped by a small obtuse corona. 



Although R. tenax is about as irregular in its branching as R. 

 floribunda and agrees with it further in the possession of numerous 

 latent branch-rudiments, the two species are totally unlike in most 

 other respects. This is seen with especial clearness when their 

 histological features are compared. In R. tenax there is a grad- 

 ual increase in the size of the cells in passing inward, the inner- 

 most cells averaging only 35 fi in width ; while in R. floribunda 

 the contrast in size between the superficial and interior cells is 

 very striking, the latter averaging 75 /x in width. The difference 



