168 Journal of the Mitchell Society [3Iarch 



5-8). Often, however, a branch arises just back of the cross wall in 

 the place of one of the clamp connections (fig. 6). In the larger 

 threads this is the only type of branching that is at all common ; but 

 from the more slender threads clamp connections are often wanting 

 and branches may arise from any point, without regard to the cross 

 wall. 



The clamp connections often develop abnormally, extending the 

 full length of the cell (fig. 7) or even joining a neighboring hypha or 

 a branch with the main hypha (fig. 8). The peculiar appearance of 

 these clamp connections is evidently M^hat gave Taubenhaus* the im- 

 pression of budding in the mycelium. 



The branches, especially those of the more slender type, often an- 

 astomose (fig. 10) and hold the hyphs together in sheets or occa- 

 sionall}^ in strands. 



The cells of the mj'celium are binucleate, at least when young. 



SCLEROTIA 



The sclerotia first appear as small white tufts of loosely inter- 

 twined small branches (fig. 1). Stained sections of such tufts show 

 an actively growing region near the periphery, which is about %o 

 of a millimeter thick, rich in protoplasm, and showing a much greater 

 affinity for stains than the center of the mass or the looser downy 

 covering which surrounds the growing region. Within a very short 

 time, 24 to 48 hours in rapidly growing material, all the cells of the 

 mass, except those of the downy covering, begin to enlarge (fig. 2) 

 and swell to about three times their former size. At the same time 

 they become vacuolate and, usually, multinucleate. The cell walls of 

 the cells in the growing region seem to gelatinize and coalesce, form- 

 ing a pseudo-parenchymatous tissue (fig. 2) about Yj millimeter thick. 

 The cells of an outer la^^er, two or three cells tliiek, now lose their 

 protoplasm ; and the cell walls turn dark, collapse to a certain extent, 

 and form a corky appearing covering over the entire surface of tlie 

 now mature sclerotium (fig, 3). The outer downy covering has be- 

 come separated by the formation of this ccrtical layer and it now 

 sloughs off, leaving the surface dark brown, smooth, and somewhat 

 shiny. The cells of the pseudo-parenchyma are broad, and more or 

 less angled, with thick colorless walls and no air spaces between; 



* Taubenhaus, J. J. Recent Studies on Sclerotium rolfsii Sacc. Jour. Agr. Res. 18: 127. 

 dIs. 3-6, fie. 1. 1919. 



