ni 



Jtcaliziii^ Hie iiiiporhiiioi to (he j»iiljlie welfare ol' iinjie cuiii- 

 plete kn()wle(ljj;e aloii*^ tln'se lines, the Peiiiisylvaiiiii Aj^ricultural 

 Experinieiit Stutioii, thr(»u.uh ils laboratory of i»hiiii [lathologj, 

 has undertaken certain investigations upon the life history of 

 /Hiiportlic pnms'itUa, in hearty eo-o])eration wilh the work of the 

 Pennsylvania Chesjnnt Tree IJIiiiht Coininission. While a com- 

 plete report cannot he made, in the natnre of the case, for a long 

 lime, we beg to snhmit a brief preliminary report on the labora- 

 tory work now being carried on by ^\v. R. A. Waldron, of the 

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

 lOxecutive Officer of the Pennsylvania Commission, a summary 

 of field studies made by Mr. R. C. ^Valton, one of the field agents 

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

 to the careful Avork of these two men. 



AIR CURRENTS AS CARRIERS OF THE CONIDIA. 



Th(^ tests were made with the blast from an electric fan, with 

 a velocity of i»erliaps twenty miles an hour. The material used 

 was bark of chestnut with tendrils of conidia projecting from 

 the months of the fruit-bodies. The tests were 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 DUiporthc pdrasitica in this 

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

 was then s(pieezed 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 det<ichment 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 l)e spread short 

 distances bv wind. 



