SOME OBSERVATIONS ON THE FORMATION OF THE 
CAPILLITIUM AND THE DEVELOPMENT OF 
PHYSARELLA MIRABILIS PECK AND 
STEMONITIS FUSCA ROTH^ 
G. R. BisBY 
WITH PLATE XXIV 
While examining preparations of Physarella mirahilis with a view 
to a study of nuclear phenomena, certain observations were made on 
the development of the capillitial threads so numerous in this species. 
In view of the fact that Physarella has not heretofore been studied 
cytologically ; and, further, since the formation of the so-called solid 
capillitium is still a matter of discussion, it seems worth while to 
publish at this time the results so far obtained. While the study was 
in progress, some fruiting specimens of Stemonitis fusca were secured, 
from which supplementary data were obtained. 
The literature pertaining to the capillitia of Myxomycetes has 
been carefully summed up by Harper ('oo, '14&) and by Harper and 
Dodge ('14a), so that it is unnecessary to give here more than a brief 
glance at earlier investigations. Harper, in his papers on the subject, 
has described thoroughly the formation of capillitium in certain 
species in which it is distinctly hollow, and was able to corroborate 
and add much to Strasburger's ('84) earlier account of the process of 
formation. In his paper on cleavage in a recent issue of this Journal, 
Harper gives incidentally some data regarding the capillitium of 
Didymium melanospermum, but does not dwell upon the methods of 
its formation. 
Materials and Methods 
Pieces of well rotted wood were collected in Prospect Park, Brook- 
lyn, in November, 191 3, and placed in covered battery jars. Upon 
this wood developed several species of Myxomycetes, the plasmodia 
of Physarella being especially abundant. Sporangia in large numbers 
were formed repeatedly, yet sufficient vegetative plasmodia usually 
1 Brooklyn Botanic Garden Contributions, No. 8. 
274 
