56 o 
Journal of Agricultural Research 
Vol. XXIV. No. 7 
Table XI shows the differences in the means of spores of biologic 
forms of stem rust grown on susceptible and resistant hosts, also the 
ratios between these differences and their probable errors. 
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fig. 9.—Differences in lengths of aeciospores, urediniospores, and teliospores of biologic forms 
of Puccinia graminis grown on susceptible and on resistant host plants. 
TabIv^ XI .—Summary of differences in the means of spores of biologic forms of P. 
graminis as affected by various host plants 
Biologic forms. 
Host plants. 
Difference in means 
(in microns). 
_ 
Difference in 
means divided 
by probable 
error of the 
difference. 
Length. 
Width. 
Length. 
Width. 
P. graminis secalis 
(aeciospores) 
P. graminis phleipra- 
tensis (uredinio- 
spores) 
P. graminis agrostis 
(aeciospores) 
P. graminis avenae 
(urediniospores) 
P. graminis tritici 
(teliospores) 
Berberis vulgaris and 
Berberis sieboldii 
Phleum pratense and 
Dactylis glomsrata 
0. 34 ±o. 24 
. 04rb . 19 
0. i6±o. 14 
. i8± . 10 
I. 42 
. 21 
I. 14 
I. 80. 
B. vulgaris and B. 
' brevipaniculata 
Avena saliva and 
Bromus tectorum 
Triticum vulgare and 
T. dicoccum 
2. 74it: . 22 
4 . 77± -22 
5 - 65 ± -59 
I. I 2 ± . II 
I. 02± . 10 
. IO± . 17 
12.45 
21. 67 
9 - 75 
10. 18 
10. 20 
• 59 
