STEMONITIS 157 



The genus is marked by its surface-net supported at the tips of the 

 dichotomously branched divisions of the columella. Over the net is 

 spread, theoretically at least, the peridial film supported by very short 

 points projecting from the net, — the peridial processes; the peridium, 

 however, is seldom seen; in some cases, certainly, is never developed. 

 Rostafinski first defined the genus as employed by recent writers. 

 Gleditsch simply renamed Micheli's Clathroidastrum; all writers 

 subsequent included species of other genera. 



The taxonomy of this genus is of the most difficult. Macroscopic, 

 defining characters are few, and even these sometimes uncertain. 

 Microscopic distinctions also tend to be illusive, variable in such 

 fashion that often at the critical point the most exact description 

 fails. All that may be done at present is to recognize two or three 

 definite types and then cautiously differentiate among these with the 

 light we have, until more general study of the group brings to service 

 a wider range of observation with more comprehensive record on 

 which judgment may better be sustained. 



We have before us many and beautiful forms of this genus yet un- 

 studied. Some of these doubtless have already found place in our 

 growing taxonomic literature ; some apparently undescribed ; all to 

 wait wider leisure or perhaps a younger hand. 



The entire life-history of every form is none too much if we would 

 set out with any hope of accuracy the genetic relationships for which 

 taxonomy stands. Recently European students are making the color 

 of the Plasmodium a basis for species-discrimination, which is good so 

 far. But plasmodic characters are at present unserviceable generally, 

 for two reasons; they vary in the same species; and unfortunately, 

 when most needed, they are unknown and inaccessible. The student 

 is generally confronted by forms mature, the plasmodic stage already 

 past. 



Key to the Species of Stemonitis 



A. Sporangia connately united. 



a. Spores verruculose 1. 5. confluens 



b. Spores reticulate 2. S. trechispora 



B. Sporangia at maturity distinct. 



a. Spore-mass grayish black. 



1. Larger, 8-12 mm. spores distinctly reticulate or warted, hut 

 sometimes nearly smooth . . . . 3. S. fusca 



