24 



All told, the insects have very much more opportunity 

 of obtaining pycnospores than ascospores, and it is not sur- 

 prising that only a very few of the colonies of the chestnut 

 blight fungus developing in the cultures originated from asco- 

 spores (17). 



MIOROSOOPIO EXAMINATION OF CENTRIFUGED 

 SEDIMENTS. 



i 



It has already been stated that, beginning with insect No. 34, 

 the original wash water of those insects yielding positive 

 results was centrifuged and given a thorough microscopic 

 examination. The sediment had been concentrated in a very 

 small quantity of water, and the entire sediment was generally 

 examined. 



The purpose of the examination was primarily to ascertain 

 whether the spores of Endothia parasitica carried were pycno- 

 spores or ascospores, this to serve as a check on the observa- 

 tions based on the rapidity of development of the colonies in 

 cultures. It was possible to find pycnospores in the sediment 

 from every insect which had yielded positive results in the cul- 

 tures. Where these results were high, pycnospores were found 

 very easily, but where the cultures indicated that only a few 

 spores of the blight fungus were carried, they were located with 

 greater difficulty, but could always be found after a reasonable 

 search. The results of these examinations are presented in 

 Table IV. It should be stated that the sediments were free 

 from dirt particles, and that the pycnospores were therefore 

 much easier to find than in the sediments from the birds (21), 

 for a considerable amount of dirt was added to the bird sedi- 

 ments as a result of scrubbing th.e feet, bill, tail, and wing 

 feathers. 



Ascospores were found to be present in the sediments from 

 only five insects, three of which were Leptostylus macula. It 

 would seem reasonable to suppose that this insect would carry a 

 considerable number of ascospores on account of its habit 

 of eating the pustules, but such was not the case, for the number 

 of ascospores found in the sediments was only a small fraction 

 of the number of pycnospores present. A probable explanation 



