51 



Eealizing the importance to the public welfare of more com- 

 plete knowledge along these lines, the Pennsylvania Agricultural 

 Experiment Station, through its lal)oratory of plant pathology, 

 has undertaken certain investigations upon the life history of 

 DiaportJtc imrasitica, in hearty co-operation with the work of the 

 Pennsjivania 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 field 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. 



Tlie 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 Avere 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 Diaporthe parasitica in this 

 material. Also, wet cotton Avas similarly held in tlie 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 tlie conidia may be detached by strong air 

 currents, and carried short distances. The detachment was 

 greater Avhen the spray played over the material. The test wdll 

 have to be carried further before quantitative results can be 

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

 bits of the tendrils nm'de 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. 



