THE DEVELOPMENT OF PYRONEMA CONFLUENS YAR. 
INIGNEUMi 
William H. Brown 
In a preliminary note (Brown, '08) and in two subsequent papers 
(Brown, '10, '11) the writer has mentioned the variety named in the 
title as a form of Pyronema confluens Tul. in which the trichogyne did 
not fuse with the antheridium. This character and several minor 
ones seem, however, to distinguish it quite sharply from the ordinary 
form, and so it has been thought better to give it a varietal name. The 
one selected has reference to the conditions under which it grows. 
A number of workers have quoted the writer as saying that there 
was no fusion of antheridium and trichogyne in Pyronema confluens, 
whereas in the note referred to (Brown, '08) it was distinctly stated 
that the form, there described, was probably derived from such a 
one as that observed by Harper ('00), in which this fusion did occur. 
The writer, as here described, has since observed this fusion in another 
form. 
Culture of Pyronema 
As the generic name implies, Pyronema confluens usually occurs on 
burnt places. Harper ('00) obtained the material with which he 
worked in abundance, on half charred masses of leaves; but also 
among damp, well decayed leaves which had not been burnt. He 
found the plant to be extremely hydrophytic, and unable to withstand 
the dryness of ordinary laboratory air for even a few hours. Harper 
notes the differences between the above conditions and those under 
which Kihlman obtained what Harper believes, from the similarity 
of morphological structures, to be the same species. Kihlman found 
his material in clefts on stones and obtained successive crops by water- 
ing the stones every three or four days. Kesaroff ('08) and Seaver 
('09) found that Pyronema grew abundantly on soil sterilized by 
heat but not on unsterilized soil. Seaver's conclusions are of special 
interest here, since, through his kindness, the writer has been able to 
repeat his experiments with the same strain and to compare it with 
^ Botanical Contribution from the Johns Hopkins University, No. 44. 
289 
