142 Alexander IV. Evans, 



cells. At the same time the small-celled layer is less definite than 

 in the axis and is rarely more than one cell thick. Toward the 

 margin a gradual increase in the size of the surface-cells is often 

 apparent, quite as in the axis, and the edges may be bounded by a 

 vague and interrupted row of cells, but there is never anything 

 distinct enough to be called a wing. The walls of the cells are 

 either thin throughout or only slightly thickened. The subterete 

 branches are broadly elliptical in section and rounded at the edges ; 

 they are about ten cells wide and eight cells thick, and the small- 

 celled superficial layer is almost as distinct as in the flattened 

 branches. 



The male inflorescences are borne on short and strongly decurved 

 branches, arising directly from the main axis or from a primary 

 branch. A male branch is usually simple but may be subdivided 

 into two or three widely spreading secondary branches. Each 

 inflorescence is terminal and occupies nearly the whole of a branch. 

 It is usually 0.5-1 mm. long by 0.6 mm. wide and apparently never 

 proliferates. The wings are three or four cells broad and crenulate 

 from projecting cells; the antheridia are usually from six to ten; 

 and the openings of the antheridial chambers are separated by two, 

 rarely by three, rows of cells. No female plants have been seen 

 by the writer. According to Stephani the female branch is very 

 short and springs directly from the main axis near the base ; it is 

 bordered by a broad and delicate, deeply papulose-crenulate wing 

 and is rounded in the apical portion. The "calyptra", still very 

 young, is described as papulose from inflated cells, but the occur- 

 rence of a corona is questioned. 



None of the preceding species show much resemblance to R. 

 Spegassiniana and R. spectabilis. Perhaps R. calva comes as close 

 to them as any, agreeing with them in the way it branches and in 

 the fact that its superficial layer is composed of relatively small 

 cells. But R. calva is a more slender species; it shows fairly 

 distinct wings, even if these are three cells thick; the difference in 

 width between the axis and the branches is less pronounced ; the 

 interior cells of the thallus average less in diameter, so that there 

 is less contrast between them and the surface-cells ; and the 

 sclerotic zone of the axis, although not very distinct, is nevertheless 

 more clearly indicated. It differs further from R. Spegazzinlana 

 in having no ventral band of narrow cells and from R. spectabilis 

 in being bounded by a single layer of small cells. 



