2 3 o RESEARCHES ON FUNGI 



the chlamydospores had access to all the oxygen contained within 

 the bell- jar. The failure of the spores to germinate in 4-6 days, 

 therefore, can scarcely have been due to lack of oxygen. Obviously 

 insufficient ventilation and insufficient oxygen are not identical 

 conditions. Ventilation includes movement of the air over the 

 surface of the culture medium, and it is possible that this movement 

 is a factor of some importance in germination. Another factor 

 which may be concerned in ventilation is the saturation of the air 

 with moisture. The spores in the stack of watch-glasses exposed 

 to the air of the laboratory must have been subjected to air which 

 was not saturated with water- vapour ; whereas, within a few hours 

 of the commencement of the experiment, the spores in the stack 

 exposed to the air contained within a closed bell- jar must have been 

 subjected to air saturated with water-vapour. Perhaps, therefore, 

 saturation of the air with water-vapour is unfavourable to the 

 germination of the chlamydospores. 



The Development and Discharge of Secondary Conidia. — As 

 we have seen, each H -shaped pair of primary conidia, while still 

 attached to the promycelium or after its fall, may put out a short 

 lateral hypha or sterigma at the end of which a secondary conidium 

 is developed, or it may produce a germ-tube which in a nutrient 

 medium may give rise to a mycelium. This mycelium grows in a 

 peculiar coiling manner, branches and rebranches for a long time, 

 and produces singly, at intervals along its hyphae, many scores or 

 even hundreds of secondary conidia (Fig. Ill, D). Normally, every 

 secondary conidium, wherever produced, is violently discharged 

 from its sterigma. The means by which this was discovered will 

 now be described. 



Some chlamydospores of Tilletia tritici were germinated on agar 

 in a Syracuse watch-glass (Fig. 113, A). On the sixth or seventh 

 day, when secondary conidia were being produced both on the 

 H-shaped primary conidia (Fig. 114, A) and on the mycelium 

 described above (Fig. 114, B and C), a suitable field was chosen and 

 a sterile glass ring was placed over it (Fig. 113, B, g). A sterile 

 cover-glass (c) was set on the ring ; and a piece of moistened filter 

 paper (/), perforated so as to allow for the free passage of the 

 microscope, was placed over the watch-glass to prevent the culture 



