Notes and Comment. 231 



louse, has been attompting for several years to work out 

 uu'thods for attacking problems in plant patbob\iiy that 

 wonhl fnrnish a sonnd, sciciitirtc basis for cb'aliiig wilh 

 plant diseases. A suuiniary of his "method echelounee" 

 was presented before the French Academy of (Sciences (12 

 June, 11) Uj. 



In studying the lUack-rot of the grape-vine, he divided 

 the fields in which the experiments were to be made into a 

 number of lots, each with one or two vines. As soon as the 

 vonnji- leaves be<jan to break out of the buds he treated one 

 lot with r>or«leaux mixture, and each day (or every other 

 day) after tlmt one lot was sprayed. The dates of the ap- 

 l)lications were recorded, and the first appearance of the 

 black-rot was noted. In ISDIJ this was on the IGth of .May. 

 Every lot had been sprayed; those that had been sprayed 

 between the 19th and iJotli of April escaped the disease; all 

 the others were attacked. The ])lants treated between these 

 t\No dates escaped because the treatment ju'^^vented the 

 germination-tube of the black-rot spore from entering the 

 leaf. The applicatiim after the 25th of April was not 

 ellicacious lu'cause the infection was already complete. 

 This method allows the exi)erimenter to determine the date 

 of the infection and duration of the incubation period — 

 that is, the time between the entrance of tlu' fungus into 

 the leaves and the breaking out of the rot upon the surface. 

 The stages in the (levelo[»m(mt of the jiarasite upon the host 

 u[» to the time of spoi-ula(i(tn were also marked off by this 

 method, and Ihese stages were then c<U'related with the 

 niet('orologi<-al condilions, so that tlie role of the atnu)S- 

 ])heric factors in tlie development of the disease could be 

 determined. These methods enabled Professor Prunet to 

 determine the ]»erio(l favorable for efficacious spraying, 

 beyond which tlie spraying was of little or no use. His 

 results also serve<l to explain the contlicting exj)eriences of 

 various vine growers with Ibu'deaux mixtui-e. The method 

 of investigation is of general application and has been used 

 in dealiuii with mihlews and the destructive "cochvlis" 

 {Conchylis amhiyiiella). 



