78 BULLETIN 957^ V. S. DEPAETMENT OF AGRICULTUEE. 



and 27, May 3, 7, and 20, June 1, and July 9. About 1,000 leaves were 

 borne on the bush on June 27 so that each half had approximately 

 500 leaves. At that time the unsprayed half had about 250 leaves 

 so heavily infected on the lower surface that some were already 

 about to fall. On the sprayed half only 10 leaves were infected, all 

 but one of these had only 1 or 2 sori, a single leaf had more. In this 

 season the fungus attacked all the Ribes bushes very heavily, more 

 so than for 10 years preceding. 



It is noted that Ewert does not say specifically that sori formed only 

 on the lower surface of the leaves. They may be presumed to have 

 done so. 



- On April 26, 1913, Ewert placed four potted plants each of Ribes 

 nigrum, R. au7'eum, and R. rubrum (var. Red Holland) around a tree 

 of Pinus strohus heavily infected with Cronartium ribicola. On 

 April 26, May 9, 17, and 24, June 6 and 21, and August 3, the several 

 plants of each species were treated as follows : 



Plant 1, sprayed mth 1 per cent Bordeaux mixture on only the upper surfaces of 

 the leaves. 



Plant 2, sprayed with 1 per cent Bordeaux mixture on only the lower surfaces of 

 the leaves. 



Plant 3, sprayed with 1 per cent Bordeaux mixture on both surfaces of the leaves. 



Plant 4, untreated check plant. 



The checks on May 17 had two leaves ynih a considerable number 

 of uredinia; on May 25 almost all leaves bore uredinia; and on July 

 28 there were 50 heavily infected leaves. 



Plants numbered 1 (sprayed on the upper surfaces only) on May 

 25, showed the first uredinia on one leaf; on June 3 six leaves were 

 infected, two very heavily; on July 28 there were 50 infected leaves. 



Plants numbered 2 (sprayed on the lower surfaces only) on June 

 3 first showed very slight infection on two leaves; on July 28 four 

 leaves were infected, all lightly. 



Plants numbered 3 (sprayed on both upper and lower surfaces) on 

 July 24 were healthy. On June 28 one leaf bore a single uredinium. 



Here again Ewert fails to state definitely whether or not the 

 infections were all on the lower surface of the leaves. 



Ewert's experiment of 1912, spraying one-half of a Ribes nigrum 

 bush, was repeated in 1913. In this case the sprayed leaves re- 

 mained healthy, except where they were not thoroughly reached 

 with the spray. This exception seems to the writer to be signifi- 

 cant, as it indicates that spraying carefully enough to control the 

 disease was apparently not practicable even for as painstaking an 

 experimenter as Ewert showed himself to be in planning and carry- 

 ing out these tests. In 1912 the disease was very virulent, while 

 in 1913 it was not. This probably largely explains the better show- 

 ing made in 1913 in these experiments. Although spraying greatly 



