EXPERIMENT STATION BULLETINS. 047 



vived and grew normally. In this experiment two tubes were taken out 

 each consecutive day after being placed in the incubator. When compar- 

 ing all the tubes after ten days, the checks which were not put into the 

 incubator at all, showed the greatest development, while the other tubes 

 indicated a gradual lesser development respectively until finally the 

 tubes taken out on the day of observation showed no development. All 

 the tubes grew normally at room temperature maintaining a difference 

 in growth as indicated by inhibition for 24 houts. That this is import- 

 ant practically, is obvious. It opens up a line of investigation which 

 might make it possible to know what kind of weather is favorable to 

 the fungus not from observation and hearsay but from actual labora- 

 tory tests. The lack of apparatus made it impossible to make these in- 

 vestigations more extensive. 



However, to determine whether this would be verified on the living 

 plant, the following experiment was performed. Two tomato plants of 

 the same age and size were inoculated in the following manner. A spore 

 suspension was made from a pure culture and one loop of this suspen- 

 sion was used for each inoculation. Twenty inoculations were made on 

 each plant, ten on the lower surface of the leaf and ten on the upper 

 surface. One plant was placed in the cool part of the greenhouse and 

 the other was placed in the warmest part of the greenhouse. The first 

 plant was placed at an average temperature of 23° C, and an average 

 humidity of 63%. (These averages obtained from Lambrecht polymeter 

 readings made several times a day). The second plant was placed so 

 that the average temperature was 28° C. while the average humidity was 

 55%. All inoculations were successful. The plant under the cooler 

 conditions showed difference in the lesions produced depending on 

 whether upper or lower surfaces were inoculated. The inoculation on 

 the upper surface gave spots 2-3 mm. in diameter, while those on the 

 lower surfaces gave larger dead areas, 4-6 mm. With the plant at the 

 high temperature, the spots produced by inoculations on the lower sur- 

 face closely resembled those of the upper surface of plant 1, while the 

 spots resulting from inoculations on the upper surfaces of the leaves 

 were mere points. Eight infections of the ten were less than 1 mm. in 

 diameter and the other two were but slightly larger. 



This experiment indicates the difference in results obtained with up- 

 per and lower surface inoculations. There is also shown the effect of 

 high temperature in inhibiting this organism while in the plant. In- 

 cidentally, this experiment indicates that a saturated atmosphere is not 

 essential for infection to take place. The small loop of spore suspen- 

 sion with which the inoculation was made, disappeared almost at once 

 when placed upon the plant. (See page 14). 



Thermal Death Point of Spores: 



This was determined by the method advocated by Novy (1899, p. 515) 

 for use with bacteria. A spore suspension in 100 cc. of sterile distilled 

 water was made using spores from a pure culture containing exuding 

 masses 2 or 3 days old. These spores were placed in a shallow dish and 

 then allowed to rise 5 or 8 cm. in a thin-walled capillary tube made by 

 drawing out a sterile glass tube of about 4 mm. diameter. After the sus- 

 pension had been drawn to the requisite height in the tube, the height 

 can be determined by the slant at which the capillary tube is held, the 



