94 



SEVENTEENTH REPORT. 



After the 18th da^- the spores no longer germinated, and although 

 7 additional tests were allowed uo further germination took place. 



A second experiment was run at a later date and aijproximately 

 the same result obtained, the spores retaining their vitality for 

 19 days. 



"\^'])ile the resistance to dessication on glass seems to be only 

 about IS days, the conditions on the plant might be much different. 

 The various materials found on the surface of seeds or on the 

 plant or fruits might enable the fungus to survive a much longer 

 period of drying in its natural environment than it would on clean, 

 sterile glass such as was used in the experiment. This has proven 

 true in the case of other organisms and the above data cannot be 

 accepted as absolutely fixing the limit of resistance to dessication. 



MAXIMUM, MINIMUM AND OPTIMUM TEMPERATUEES. 



The apparatus for this experiment consisted of a metal box hav- 

 ing a compartment in one end filled with ice and one at the other 

 end filled with water, kept heated by an incandescent lamp. The 

 space between the two was divided into compartments, thus getting 

 varying degrees of temperature as follows. 



8°C. 

 11° C. 

 24° C. 

 29° C. 

 34° C. 

 43° C. 

 51° C. 



These temperatures were maintained within one degree. Test 

 tubes of cucumber agar inoculated with the fungus were placed in 

 each of these compartments and the amount of growth, if any. 

 observed. 



TABLE IT. 



