304 Proceedings of Indiana Academy of Science 



The above description agrees closely with that given by Sherbakoff 

 for P. terrestris, and since the symptoms on the tomato were identical 

 with those described by the same author for buckeye rot of tomato, the 

 organism causing the disease in Indiana is in all probability that species. 



Inoculations. — Inoculation work was done in the field late in the 

 summer of 1921 with cultures of the Phytophthora isolated from toma- 

 toes. Eighteen eggplant fruits were inoculated by making a very slight 

 wound on the surface of the fruit with a flamed scalpel and placing 

 very small pieces of mycelial growth from agar cultures on the wounds. 

 Nine of the 18 inoculated fruits developed the rot, from which the same 

 Phytophthora was later reisolated. 



Thirteen pepper fruits were similarly inoculated and ten of the 

 13 inoculated fruits developed the rot. Six pepper fruits were inoc- 

 lated by placing fragments of an agar culture on the unwounded sur- 

 face and four of the six developed the disease. The fungus was reiso- 

 lated from these infected fruits. 



Inoculation of green tomato fruits in moist chambers in the labora- 

 tory, both with and without wounding the suiface, by placing fragments 

 of agar cultures on the surface of the fruits and over the wounds, pro- 

 duced a typical Phytophthora rot. 



The inoculation of six small watermelon fruits by making a slight 

 wound near the blossom-end and placing small blocks of agar cultures 

 over the wounds gave negative results. 



On Nov. 30, 1921, potatoes were surface sterilized, sliced with a 

 flamed scalpel and placed in sterile moist chambers and inoculated by 

 placing mycelium from an agar culture on the cut surface and incubated 

 at 23 "C. and 21° Q. No infection occurred. 



Temperature Relations. — A series of cultures was grown at diff'erent 

 temperatures to determine the optimum temperature for the mycelial 

 development of the organism. A very small block of an agar culture 

 was planted in the center of each of a number of poured jilates of potato 

 agar. These plates were then placed in moist chambei's and 

 incubated at the following temperatures: 8°-9°, 12°, 15°, 20°, 23°, 27°, 

 30°, and 35 °C. Measurements of the diameter of the colonies were 

 made at different intervals. The measurements made at the end of nine 

 days are given in table 1. 



TABLE 1. Growth of P. terrestris at Different Temperatures. 



8-9 °C. 



No growth. 



12°C. 



20 mm. 



15°C. 



30 mm. 



20 °C. 



32 mm. 



27°C. 



35 mm. 



30 °C. 



50 mm. 



35°C. 



32 mm. 



From the above table it is evident that the optimum temperature 

 for mycelial development is about 30 °C. and that low temperatures are 

 not favorable to its development. (These temperature relations are 

 illustrated in fii^-ure 2, C.) 



