1917] Butters,— Studies in Ferns — Botrychium 215 
Key to the American species and varieties of the BOTRYCHIUM VIRGINIANUM 
group. 
A. Ripe sporangia straw colored, opening but slightly in dehiscence, their 
walls composed of regular cells; pinnules of the sterile frond ovate 
to lance-ovate, their ultimate segments spatulate. 
B. Sporangia 1-1.8 mm. long, segments of sterile frond imbricated. 
B. virginianum var. laurentianum. 
BB. Sporangia 0.5-0.8 mm. long, segments of sterile frond not imbricated. 
B. virginianum var. intermedium. 
AA. Ripe sporangia brown, opening rather widely in dehiscence, their walls 
composed, at least in part, of irregular cells with sinuous walls. 
C. Fertile shoot much longer than the sterile frond, no additional 
sterile leaf present at the time of fruiting. 
D. Sporangia with conspicuously broad herbaceous bases. 
B. virginianum var. occidentale. 
DD. Sporangia narrow at the base. 
E. Sporangia 0.7-0.8 mm. long, dark brown, concolorous, their 
valves recurved in dehiscence. 
F. Pinnules of sterile frond but slightly dissected, cordate or 
truncate at base, valves of sporangia moderately recurved. 
B. virginianum var. meridionale. 
FF. Pinnules of sterile frond much dissected, cuneate or decur- 
rent at base, valves of sporangia strongly recurved. 
B. virginianum. 
EE. Sporangia 0.7-1.2 mm. long, their valves light brown with a 
darker margin, valves usually not recurved in dehiscence. 
B. virginianum var. europaeum. 
CC. Fertile shoot but little longer than the sterile frond, an additional 
sterile leaf present at time of fruiting.............. B. cicutaria. 
Again, as in the case of Athyrium Filix-femina and its allies an 
examination of the close technical characters of Botrychium virginia- 
num shows that it is readily divided into natural varieties, and these 
are found to have a distribution entirely in harmony with what is 
known concerning the laws of the distribution of Phanerogams and 
indeed, very similar to the distribution of the Filix-femina group. 
Thus we find Botrychium virginianum occurring in the deciduous 
forests of eastern North America, and again, in this case entirely 
unchanged, in eastern Asia,— both in China and in Japan. Again 
we find the European plant reappearing unchanged in the Pacific 
northwest of America, and in this case occurring eastward across the 
continent in the evergreen coniferous forests. 
In Japan there is one local variation from the typical form of the 
species (B. strictum), and in eastern North America there are at least 
