696 



MEDICAL MYCOLOGY 



to form incomparably larger masses, making it difficult to believe that they 

 have any relation to spores or to nuclei. Quite possibly this represents a waste 

 product, since its abundance is always connected with advanced degeneration. 

 While the mycelium is very uniform throughout the genus, there is very 

 great diversity in spore formation. The spores are developed by a transfor- 

 mation of more or less specialized hyphal branches, early distinguishable from 

 sterile hyphae of the aerial mycelium. In general, the diameter of any por- 

 tion of sterile mycelium is attained at the time it arises through the elongation 

 of the growing hyphal tip. The sporogenous branches are, in the beginning. 



Fig. 112. — Actinomyces II isolated from soil. 1, portion of aerial mycelium, showing 

 conspicuous septa in fertile branches and the relation of the latter to axial filaments ; 2-6, 

 stages in the development of a fertile hypha (X2,750). (After Drechsler 1919.) 



conspicuously thinner than the axial hyphae from which they are derived. 

 Later, when they have reached nearly their full length, they increase in thick- 

 ness, the extent of this varying much with individual species. 



In most species the maturation of the sporogenous hyphae is associated 

 with a peculiarity in growth by which they become coiled in more or less 

 characteristic helices. The tendency toward a coiled condition is usually 

 clearly manifest before the branch has grown to half its length through the 

 open flexuous habit of the young filament. As elongation continues, the turns 

 become increasingly definite, but the contraction leading to the final condition, 

 which ranges from Actinomyces XIII, with its open, barely perceptible turns, 



