388 BOTANICAL GAZETTE [November 



entirely by spores; and since the prothallia are of the subterranean 

 tuberous type, with an endophytic fungus, the prothallia develop 

 only when the conditions for this rather unusual mode of develop- 

 ment are present. 



How far the spores might be carried is problematical. The 

 grouping of plants indicates that most of the spores are not carried 

 far, but when a plant is once established it becomes the center of 

 a group. 



At first I was interested only in the fact of grouping and in the 

 size of the groups of Botrychium obliquum and B. Virginia num. 

 It was noted immediately that the groups of B. virginianum 

 contained many more plants than those of B. obliquum, and that 

 the groups were more closely associated. In counting plants and 

 making plots, one soon learns to find specimens, especially the 

 smaller ones, which easily escape notice, and the number of plants 

 in a group is likely to be surprisingly larger than the average 

 botanist would have guessed from a cursory examination. 



The most closely associated groups, with the largest number of 

 plants in a group, were found at the borders of rather open woods. 

 Plants in the deeper woods, although likely to be large and vigorous, 

 are not abundant. 



During the Septembers of the past four years the grouping was 

 observed, and a searching for prothallia developed some facility 

 in recognizing young plants. In 1918 the plants of many groups 

 were counted, especially at Sullivan, where Botrychium is excep- 

 tionally abundant; and in 19 19 plots were made, showing not only 

 the number and position of plants in a group, but also the relation 

 of the groups to each other. 



Botrychium virginianum is more abundant than B. obliquum, 

 even when the two species are growing together under the same 

 conditions. On the eastern border of a densely wooded tract at 

 Sullivan, Ohio, where B. virginianum is more abundant than I 

 have ever seen it in any other locality, prothallia were collected 

 and observations were made for several years. The border of the 

 woods is roughly marked by a rail fence, with but few trees on the 

 eastern side and some trees removed on the western side, so that 

 the woods end in what farmers call a "clearing." The plants and 



