51 



Realizing the importance to the public welfare of more com- 

 plete knowledge along these lines, the Pennsylvania Agricultural 

 Experiment Station, through its laboratory of plant pathology, 

 has undertaken certain investigations upon the life history of 

 D'mportlH' ixinixiticd, in hearty co-operation with the work of the 

 Pennsylvania Chestnut Tree Blight Commission. While a com- 

 plete report cannot be made, in the nature of the case, for a long 

 time, we beg to submit a brief preliminary report on the labora- 

 tory work now being carried on by Mr. R. A. Waldron, of the 

 Experiment Station staff; to which is added at the request of the 

 Executive Officer of the Pennsylvania Commission, a summary 

 of Held studies made by Mr. R. C. Walton, one of the field agents 

 of the Commission. Credit for the findings reported here is due 

 to the careful work of these two men. 



AIR CURRENTS AS CARRIERS OF THE CONIDIA. 



The tests were made with the blast from an electric fan, with 

 a velocity of perhaps twenty miles an hour. The material used 

 was bark of chestnut with tendrils of conidia projecting from 

 the mouths of the fruit-bodies. The tests w r ere made with these 

 tendrils dry, with them moist, and with the spray from an atomi- 

 zer playing over them, the last to imitate conditions prevailing 

 during storms. The attempt was made to catch the spores on the 

 surface of sterilized potato agar exposed about six inches away, 

 in the blast; and to determine the carrying power of the air cur- 

 rent from the subsequent growth of Diaporthc pnmxitk-a in this 

 material. Also, wet cotton was similarly held in the blast; it 

 was then squeezed out in sterile water; this was centrifuged, and 

 microscopic examination made of the sediment, as well as cul- 

 tures from it. There was unmistakable evidence, from each 

 line of testing, that the conidia may be detached by strong air 

 currents, and carried short distances. The detachment was 

 greater when the spray played over the material. The test will 

 have to be carried further before quantitative results can be 

 given. It seems likely that the detachment was largely of small 

 bits of the tendrils made up of large numbers of spores, and that 

 these are too heavy to be carried great distances; and suggests 

 that under natural conditions infection may be spread short 

 distances by wind. 



