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BULLETIN 934, IT. S. DEPARTMENT OF AGRICULTURE. 



either of tlie groups of pots compared is seriously affected by parasites, the 

 most convenient index of the comparative activity of the fungi used. In such 

 a comparison as that between the Rheosporangium pots and the controls in 

 experiment 68 (Table VII), accidental variations in emergence, of course, over- 

 shadow the slight effect of the fungus, and the definitely determinate per- 

 centage of loss after emergence is the only value which can serve as a basis for 

 any definite conclusion. 



TABLE VII. Results of inoculations on pine seedlings icith initial and reisolated 

 strains of Rheosporangium aphanidennatus contpared with parallel inocula- 

 tions with Pythium- deuaryanum. 



A frequency graph based on the survivals of the 50 individual pots 

 inoculated with Rheosporangium in experiment 68 yields a rather 

 interesting asymmetrical curve (fig. IT). The shape of the curve 

 is taken as indicating that in a large number of the pots the inocula- 

 tion produced no effect, while in the smaller number of pots in which 

 the inoculation apparently " took," the loss was rather heavy. This 

 is a rather common phenomenon in inoculations which are only 

 partly successful, part of the pots being free or practically free from 

 loss, while others are nearly cleaned out. It will be seen again in 



