546 
J ournal of Agricultural Research 
Vol. XXVIII, No. 6 
The aeciospores (PI. 1, D) are predominantly spherical to subspherical in 
shape, the modal length-to-width ratio being approximately 1.1 to 1. The 
thickening of the upper wall, in vertical section of the sorus, described by Rosen 
and Kirby ( 9 ) as characteristic of the aeciospores of P. graminis, was quite 
evident. There is some indication of a positive correlation (.194 ±.0649) between 
the length and width of these spores (Table VI), but it probably is too small to 
be considered statistically significant. 
There is clearly no correlation (.038±.0673) between the two diameters of the 
urediniospores (Table VII). These spores are for the most part subglobose 
(PL 1, F), resembling the urediniospores of P. graminis avenae on Bromus tec - 
torum L. (11, p. 62), and the predominating length-to-width ratio is about 1.1 to 1, 
Tabi^e V.— Correlation table for 100 teliospores of Puccinia graminis poae. Spore 
length , subject; spore width, relative. Coefficient of correlation = —.613±.0421 
Spore Width 
11m 
13m 
15m 
17m 
19m 
21m 
20m 
5 
2 
1 
8 
| 30m 
1 
13 
17 
3 
1 
35 
55 
40m 
1 
9 
17 
11 
2 
40 
H 
I so* 
10 
4 
14 
60m 
2 
1 
3 
4 
19 
35 
33 
7 
2 
100 
Table VI.— Correlation table for 100 aeciospores 
of Puccinia 
graminis 
poae . 
Spore length, 
subject; spore width, relative . 
Coefficient of correlation = 
o> 
vs 
II 
±.0649 
Spore Width 
Hm 
12m 
13m 
14m 
15m 
12m 
1 
l 
2 
13m 
2 
9 
11 
h 14m 
2 
3 
9 
8 
20 
55 
g 
A 15m 
2 
4 
11 
11 
3 
31 
« 
2 16m 
m * 
1 
3 
10 
5 
2 
21 
17m 
1 
1 
3 
4 
2 
11 
18m 
1 
1 
2 
4 
5 
14 
43 
29 
100 
