MICHIGAN ACADEMY OF SCIENCE. 299 



heginiiing- of a spore, but further development has not been found. These 

 cells may perhaps be chlamydospores. The branching habit is poorly 

 develoi^ed in this mycelium, anything more than a primary branch seldom 

 appearing (PI. XIII, Figs. 19 and 20). 



Upon agar media kept under humid conditions, newly formed spores 

 may germinate directly. In the center of the colony where the growth 

 is very dense, many of tlie germ tubes sent out at once differentiate into 

 conidiophores and bear spores. (PI. XIII, Fig. 5.) These newly formed 

 spores are somewhat smaller than the spore from which they arise, 

 ranging in size from 18-21 microns x 11-18 microns. As many as six of 

 these conidiophores varying in length from 12 to 58 microns, have been 

 observed arising from a single spore. This direct spore formation, i. e., 

 from spore to spore without any vegetative mycelium intervening, may 

 be due to the inability of the germ tube to penetrate the dense mass of 

 growth which lies below it, so that the agar, — the source of food, — cannot 

 be reached. If this is the case, such direct spore formation may be 

 the result of starvation. Near the edge of the colony the germ tubes have 

 ready access to the fresh, unoccupied agar, hence vegetative mycelium is 

 produced. 



It was noted that in the foregoing spores giving rise directly to the 

 new spores were not attached to the conidiophore upon which they were 

 originally borne. It was thought that the humidity of the surrounding 

 atmosphere might have something to do with the falling of these spores. 

 To determine this, the following experiment was performed: 



Some petri dish cultures containing numerous, small, closely crowded 

 colonies, and iii wliich the agar was completely dried out, were used. 

 These were kept in an inverted position for a day or so, that any spores 

 that nn'ght fall naturally might be removed. One of these dishes was 

 then suspended in an inverted position over a freshly poured dish of 

 agar, so that any falling spores would be caught. This arrangement 

 was then placed in a deep culture dish in the bottom of which was a 

 little water. A similar arrangement was placed in a deep culture dish 

 without any water, that is, in a relatively dry atmosphere. When exam- 

 ined after ten days the agar imderneath the dish in the moist chamber, 

 bore colonies corresponding almost exactly with the location of the 

 colonies in the inverted dish suspended above it, indicating tliat the spores 

 had been dropped off. The lower dish of agar in the dry chamber con- 

 tained no growth. The results of this experiment indicate that the humid 

 atmosphere is one of the factors involved in tlie release of the spores 

 from their conidiophores. This release of the spores may be of the type 

 of ejection similar to that noted in the rusts (Coons 1912) and other 

 fungi. 



