564 



Journal of Agricultural Research 



Vol. Xni, No. II 



Table IX. — Summary of results of inoculation experim,ents with Coccomyces spp.from, 

 Prunus spp., Madison, Wis., igi6 and igij ^ 



[The average degree of infection is represented by the average of the numbers representing the severity of 

 infection from the individual inoculations which gave positive results (see footnote c. Table I). The 

 results of series in which the maxiramn infection is represented by a number less than 3 and those which 

 represent the combined infection from two or more inoculations (see footnote j. Table II) are not included]. 



Plant inoculated. 



Results with strains from — 



P. cerasus. 



P. avium. 



P. ntaha- 

 leb. 



at 



M g 



a> 



P. penn- 

 sylvanica. 



P. domes- 

 tica. 



P. Tiirgin- 

 iana. 



P. sero- 

 tina. 



OJ o 



2.9 



cerasus 



avium 



■mahaleb 



pennsylvanica . . . 



serotina 



padus 



Tjirginiana 



dcrmestica 



insilitia 



americana 



salicina 



munsoniana .... 



cerasifera 



persica 



persica nectarina 



armeniaca 



besseyi 



(<:) 



(<^) 



1.4 

 4.0 



o Compiled from Tables I-VIII. 



6 All inoculations in which the fungus induced lesions and fructified are listed as positive. Cases of 

 flecking and spotting without fructification are listed as negative. Cases in which the results of successive 

 inoculations on the same plant were indistinguishable are treated as single inoculations. 



« The number of experiments was limited by the failure of experimental plants to take root. 



<* Inoculated by ascospores applied by natural discharge. See' discussion, p. 550. 



« Positive results were obtained from greenhouse experiments only. 



DISCUSSION OF RESULTS 



A perusal of Table IX, which contains a summary of the results of 

 the experiments of 191 6 and 191 7 will show that in no case did the 

 strains from any two host plants give identically the same results. The 

 results from strains from P. cerasus, P. avium, and P. mahaleb differ 

 only very slightly, however, and from the standpoint of host relation- 

 ships the strains from these species may clearly be grouped together. 

 The strains from P. cerasus readily and consistently infected P. cerasus, 

 P. avium, and P. mahaleb, while in certain cases, and apparently with 

 difficulty, they infected P. insilitia, P. munsoniana, P. cerasifera, and 

 P. besseyi. The strains from P. mahaleb induced infection on all the 

 plants just mentioned, except P. cerasifera, upon which they were not 

 tested. In addition, however, they also infected P. pennsylvanica. 

 This is the only important regard in which their results differed from 

 those of strains from P. cerasus and P. avium. It must be borne in 

 mind, however, that, owing to the failure of experimental plants to root, 

 the number of tests with strains from P. cerasus and P. avium on P. 



