048 STATE BOARD OF AGRICULTURE. 



ODd whicli dipped in the suspension was sealed in the flame of a micro- 

 burner. Then the cajtillary tube was scratched with a file about half an 

 inch beyond the liquid, broken and sealed. At one time about two dozen 

 such spindles were prepared, and were ready for use in the experiment. 

 The use of such small quantities of spore suspension in thin-walled tubes 

 enables the entire mass to reach the desired temperature quickly after 

 submersion in the water bath. 



A series of water baths made of heavy cast iron were filled with water 

 at the desired temperature. Each bath was equipped with a Bunsen 

 burner. By varying the height of the flame and frequent observations, 

 it was possible to maintain the temperature within the range of I/2 de- 

 gree. Temperatures ranging from 40° to G0° C. by gradations of 2\<2 

 degrees were used. After an exposure of ten minutes the spindles were 

 removed and dropped into cold water. A nick was filed near one end, 

 then the tubes w^ere rinsed in HgCL, followed by two changes of sterile 

 water. One tip was broken off with flamed forceps. By gently heating 

 the unbroken tip the contents of the tube were quickly forced out into 

 the test tubes of media. The results were as follows : 



TABLE 3.— THERMAL DEATH POINT OF SPORES: TEST WITH CAPILLARY TUBES 



It may be concluded that the spores will not grow after being sub- 

 jected to 521/2 degrees for ten minutes. However, it is worthy of note 

 that the number of spores which germinated and grew in tubeis 40° — 

 421/2 — iS, were much more than that of 47l^° and 50. At 50 only 6 

 colonies grew; at 47i/^, 15 colonies, while at 40 — 42% — 45, the growth 

 covered the entire surface of the medium and appeared exactly similar 

 to check tubes. This resistance of certain spores raises the question 

 whether these spores are especially heat resistant due to protoplasmic 

 properties and whether the growing of these would give a heat resistant 

 strain. This unfortunately could not be followed to a conclusion. 



Relation to Light: 



The Influence of Sunlight: 



Three plates of cornmeal agar were poured using exuding spores from 

 a pure culture. Two plates were exposed to the sun for three hours. 

 After three days colonies were in evidence, with no perceptible difference 

 in growth of exposed plates and check. Five inoculations were made on 

 young tomato plants and exposed to the sun from 11:00 A. M. to 2:00 

 P. M. Five inoculations were made as checks. The inoculated plants 

 developed typical infection, showing that for a period of at least three 

 hours the sun had no effect upon the development of the organism. This 

 verified the results obtained by exposing the spores in poured plates of 

 cornmeal agar for the same length of time. 



Comparison of Growth in Light and Dark: 



Fourteen tubes of nutrient glucose agar were inoculated with exud- 

 ing spores from a culture upon tomato agar. Seven tubes were wrapped 

 in black paper (such as is used to cover photographic films). These 



