246 
Journal of A gr {cultural Research 
Vol. XXV, No. 5 
maining plants were all transplanted to the field, where they also were 
selfed and crossed in the spring of 1922, thereby furnishing considerable 
material for further study. 
Table I .—Number of seeds of rye obtained by selfing and by crossing plants 7, 8 , g, and 
10 in various combinations 
Plant 
No. 
Treatment. 
Number of 
heads.® 
Number of 
kernels 
produced. 
7 
8 
Selfed.. 
2 
8 
.do... 
2 
O 
9 
10 
.do. 
2 
O 
.do. 
5 
1 
3 
0 
7 
7 
• 7 
8 
Crossed by 8.. 
Crossed by 9. 
2 
y 
6 
Crossed by 10... 
1 
17 
1 5 
16 
Crossed by 7. 
x 
8 
Crossed by 9.. 
5 
2 
0 
Crossed by 7.. 
y 
0 
Crossed by 8. 
5 
1 
46 
A 
y 
10 
Crossed by 7... 
nr 
Total. 
229 
« The remaining heads in all cases were open-fertilized and produced a total of 367 seeds. 
Material differences were found in types of susceptibility in the speci¬ 
mens studied. Nearly all kinds of intergradation between extreme sus¬ 
ceptibility and practically complete immunity were noted. These, 
however, may be divided into about nine main types as shown in Plate 
2, A-I.® Thus one group showed a high susceptibility (PI. 2, A) as indi¬ 
cated by the very large size and dark color of the uredinia, approaching 
in appearance those of Puccinia graminis. Under greenhouse conditions 
this type usually produced from the outer portion of the mycelium a 
more or less perfect ring of uredinia encircling the one or two first formed. 
Another group (PI. 2, B) showed a somewhat less vigorous development, 
the uredinia being smaller, somewhat lighter in color, and the encircling 
uredinia being produced less frequently. A few individuals, having a 
type of susceptibility very similar to the last, showed also a few small 
uredinia in hypersensitive areas (PI. 2, D). This condition may possibly 
indicate the presence of more than one strain of the rust in the culture 
used or may represent a distinct type. Another group (PI. 2, E) had 
uredinia of fair size similar to the preceding, differing in that, while 
the host tissue in the infected areas did not show any especially deleterious 
effect, the tissue immediately surrounding these areas became chlorotic 
and in some cases brown, resulting in the infected areas appearing as 
green islands. Another group (PI. 2, C), although having fairly large 
uredinia, showed a lack of normal adjustment between host and rust in 
the more or less mottled or chlorotic condition of the host in the infected 
areas. All of the remainder showed pronounced resistance as indicated 
by hypersensitive areas which developed in the infected spots. There 
a Plant 8 (PI. 1, B) is of the same type of susceptibility as that shown in Plate2, 1 ; plant 9 (PI. 1, A) as that 
in Plate 2, H: plant n (PI. 1, E) as that in Plate 2, E; plants 7 and 10 (PI. 1, C, D.) as those in Plate 2, 
A or B. Leaves of the parent plants 7, 8, 9, and 10 were photographed natural size, shortly after infection 
had appeared, while the types given in Plate 2 were photographed, enlarged two diameters, after the rust 
had reached its fullest development. This accounts for the single scattered uredinia shown on the suscep¬ 
tible parents and the encircling uredinia in type A, Plate 2. 
