May 10,1924 
Pucdnia graminis in the United States 
543 
The host range of P. graminis poae appears to be narrow. According to 
Eriksson (2 and 8) and Jaczewski (5), this rust variety is restricted to the genu* 
Poa. If this is true it is the only variety of P. graminis now known to occur in 
the United States which infects species of a single genus only. However, it 
probably can infect, at least weakly, members of other genera, because minute 
uredinia developed on barley (Table II). Extensive inoculations are now under 
way in order to ascertain the infection capabilities of the rust. 
Morphologically, also, the variety poae is quite distinct, the spores being 
characteristically small. The urediniospores, teliospores and aeciospores are 
considerably shorter than those of any other variety, but they do not differ so 
much in width. Tables III and IV present the measurements of the three kinds 
of spores of P. graminis poae and a comparison of these with those of the other 
varieties of P. graminis. 
Table III. — Variations and constants for length and width of the various spores 
of Pucdnia graminis poae grown on congenial host plants and under favorable 
environmental conditions 
Kinds of spores 
Spore 
diam¬ 
eters 
Spore classes 
» 
Mean 
Standard 
deviation 
Coefficient 
of vari¬ 
ability 
Teliospores from 
Poa compressa— 
Length. 
20m 
30m 
40m 
50m 
60m 
100 
36.904=0.62 
9.13±0.44 
24.744=1. 25 
8 35 40 14 3 
Width. 
11m 
13m 
15m 
17m 
19m 
21m 
100 
15.52:4=0.14 
2.074=0.10 
13.34=1=0.65 
4 19 35 33 7 2 
Aeciospores from 
Berber is vulgaris- 
Length. 
12/t 
13m 
14, 
a 15m 
16m 17 
ft 18m 
100 
15.07 ±0.09 
1.35=1=0.06 
8.96:4=0.43 
2 11 20 31 21 11 4 
Width. 
llM 
12m 
13m 
14m 
15m 
100 
13.234=0.07 
0.974=0.05 
7.33=fc0.35 
5 14 43 29 9 
Uredinio spores 
from Poa com¬ 
pressa .. 
Length. 
15#t 
17m 
19m 
21m 
23m 
100 
18.64=fc0.10 
1.51 ±0.07 
8.104=0.39 
1 35 46 17 1 
Width. 
13m 
14m 
15m 
16m 
17m 
18m 
100 
15.784=0.07 
1.06db0.05 
6.72db0.32 
3 12 14 48 21 2 
Table IV. — Summary of differences between the means of the dimensions of the 
various spores of Pucdnia graminis poae and those of other varieties of Pucdnia 
graminis 
Teliospores 
Aeciospores 
Urediniospores 
Diam¬ 
eters. 
Biologic forms compared. « 
Difference 
in means 
(in microns) 
Differ¬ 
ence di¬ 
vided 
byP.E. 
Difference 
in means 
(in microns) 
Differ¬ 
ence di¬ 
vided 
byP.E. 
Difference 
in means 
(in microns) 
Differ¬ 
ence di¬ 
vided 
byP.E. 
P. graminis tritici .. 
14.90=1=0. 79 
18.86 
4. 654=0. 21 
22.14 
13. 764=0. 21 
65.52 
-*-3 
42 P. graminis secalis . 
•S P . graminis avenae _ 
10.45±0. 77 
13. 57 
2.03 ±0. 21 
9.67 
8 . 504=0.17 
50.00 
b£> 
(3 
9.25=1=0. 75 
12.33 
3. 554=0.14 
25.36 
9.864=0.18 
54. 78 
<X> 
| ^ P. graminis phleipratensis. 
£ s P. graminis agrostis . 
4.40=1=0. 70 
3.40=1=0. 74 
6.29 
4.59 
1.394=0.20 | 
| 6.95 
5. 314=0.16 
3. 734=0.16 
33.19 
23.31 
■g § P. graminis tritici-- . 
^ P. graminis secalis .. 
g P. graminis avenae __ 
P. graminis phleipratensis. 
P. graminis agrostis .. 
1.15=1=0.18 
6,39 
2.434=0.12 
20.25 
4.01 ±0. 09 
44.56 
& 
0. 75±0.18 
4.17 
0. 204:0.13 
1.54 
1.414=0. 09 
15.67 
'O 
0. 32=h0.18 
1.78 
1.47 ±0.12 
12.25 
4.164=0.10 
41. 60 
5 
0.11=1=0.17 
0 . 88=1=0.18 
0.65 
4.89 
0. 25 ±0.11 
| 2.27 
1.104=0. 09 
0.104=0. 09 
12.22 
1.11 
a Data on forms other than P. graminis poae from Levine (6). 
