550 
Journal of Agricultural Research 
Vol. XXIV, No, 7 
It is that the tritici form possesses the longest urediniospores, the agrostis 
form the shortest, and the rest group themselves between these two 
extremes. 
TabliS VI .—Urediniospore dimensions of biologic forms of P. graminis as given by 
various authors 
Authority. 
P. graminis 
tritici. 
P. graminis 
secalis. 
P. graminis 
amenae. 
P. graminis 
phleipra¬ 
tensis. 
P. graminis 
agrostis. 
Eriksson and Henning (j, p. 124 
and 13d) ... 
29-43X1S-21 
31-33X18. IS 
37.85X22.76 
23-38X15-22 
22-40X16-21 
18-27X15-19 
Freeman and Johnson {4, p. 2?)^.. 
Stakman {12, />. 27)^. 
Stakman and Jensen (ij, p. 27?)*.. 
19-35X16-24 
19-37X14-26 
17-31X15-23 
16-32X12-21 
Stakman and Levine {14, p. 4gp,. 
23-42X15-25 
18-39X13-21 
15-32X12-20 
1 These figures represent averages, size limits not having been given. 
* Decimal fractions have been converted to the nearest integer. 
It will also be noted by examining the graphs and the measurements 
quoted that P. graminis secalis and P. graminis avenae differ but little 
in spore length, while the spore width of the latter is much the same as 
that of P. graminis tritici. It will be noted further that according to 
the graphs as well as the quotations, there is a similarity in the width 
of the urediniospores of the secalis and phleipratensis forms, but the two 
diverge noticeably in length. The constants, given in the second section 
of Tables III and IV, and the differences in the means, presented in 
