122 



A difference of 0.97^.28 between the means of two samples from the 

 same specimen (Nos. 52 and 53) a difference more than three times the 

 probable error shows clearly the difficulties of sampling, and that such 

 differences between samples of the same species grown under the same con- 

 ditions may be expected. The differences in several instances, notably 

 between Nos. 44 and 49, 44 and 48, and 46 and 51, are no greater than those 

 between two samples of the same specimen and may well be due to sampling, 

 and to this extent show the fungus, over a wide geographic range, to be 

 remarkably uniform. In several other instances, however, there is a wide 

 difference of means, above the probable error notably in all cases involv- 

 ing sample No. 53. These differences are often four, five, or six times the 

 probable error, and occasionally run as high as eleven or twelve times the 

 probable error even with this remarkably uniform fungus. While these 

 differences may in part be attributed to sampling they probably represent 

 also morphological changes due to environmental differences, and differ- 

 ences of nutrition or humidity, but do not necessarily indicate racial dif- 

 ference in the fungus. 



To determine whether various cereals, autoclaved, influence conidial 

 length differently, plates of H. No. 1 were prepared under standard condi- 

 tions except that in the same Petri dishes were placed shoots of wheat, rye, 

 barley and corn. The resulting graphs of conidial length are given in Fig. 

 M. The differences in means are as follows: 



On rye and wheat, 0.40 .29 

 On rye and corn, 0.45 .20 

 On wheat and corn, 0.02 .22 



The mean length on rye, corn, and barley is in close agreement with 

 that on wheat, and, apparently, under these conditions the species of 

 shoots counts for little in its influence on conidial length. 



Conidial-length graphs (Fig. N) made from H. No. 1 grown on fresh 

 wheat-stems, on young wheat shoots, on wheat leaves, and on young wheat 

 plants, all autoclaved in test-tubes with a few centimeters of water, show a 

 considerable increase over those under standard conditions (Graph 42, 

 Fig. K) ; also, in Graphs 58, 60, and 61 (Fig. N), they show a much larger 

 standard deviation and coefficient of variability, probably due to the va- 

 riable humidity under these conditions. The small number of conidia 

 measured, and the lack of control over humidity may be presumed to ac- 

 count for such variation as is seen. 



Live wheat inoculated in rag doll showed at the 6th day 100% infec- 

 tion. These infected seedlings were placed in a Petri dish on moist filter- 



