170 
Journal of Agricultural Research y 0 i. xxvm, No. 2 
Table II.— Occurrence of “brittle” plants in selfed-str ains of rye, in 1922 
1922 culture number 
Years selfed 
Normal 
plants 
Brittle 
plants 
R U. 
1, D-P «. 
28 
2 
R 19. 
1, D-P.. 
17 
5 
R 36. 
1. 
6 
3 
R 37... 
1. 
5 
1 
R 39. 
D-P b . 
12 
6 
R 41. 
1. 
16 
2 
R 43... 
D_P 
14 
7 
Total. 
98 
26 
a 1 , D-P=one year selfed followed by D-P. 
b D-P=intercross, that is, two heads on different plants in the same culture bagged together. 
Chemical analysis of the plants was undertaken to determine the cause of 
brittleness. Samples of brittle rye and normal rye were put up while green in 
85 per cent ethyl alcohol containing sufficient Ca(C0 3 )2 to neutralize any acids. 
Table III.— Analysis of normal and brittle rye culms 
Sample 
Dry 
weight 
Per 
cent 
ash 
Sugar 
Pen¬ 
Starch 
Total 
Crude 
(dry 
basis) 
Fiber 
(wet 
basis) 
Red 
Sucrose 
Total 
tosans 
pectin 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Brittle rye. 
27.03 
5.49 
7.09 
6.47 
13.57 
34.34 
0.78 
0.234 
13.50 
\ 3.81 
Do... 
5.44 
7.12 
6.50 
13.60 
33.35 
.81 
.242 
14.75 
Normal rye. 
40.58 
4.91 
5.60 
4.63 
10.26 
25.40 
.98 
.20 
32.21 
} 13.04 
Do..... 
4.85 
5.67 
4.79 
10.42 
24.60 
1.04 
.20 
32.10 
In Table III a comparison of the principal chemical constituents which may 
be associated with the production of brittle or healthy plants is given. The 
percentage of dry weight of the brittle rye and of the normal rye shows quite an 
appreciable difference. The brittle rye contains the lower percentage of dry 
material. This suggests a high content of colloid with high water-holding capac¬ 
ity, a condition which is indicated by the greater pentosan content of the brittle 
plants. Culms that had a high water content or were turgid would have a tend¬ 
ency to snap off easily as the brittle plants do. 
The crude fiber determination shows the relative amount of skeletal material 
of the plants, particularly cellulose and lignin, which are responsible for the 
strength of the culm. There is a ratio of 32.15 per cent crude fiber in the normal 
plants to 14.13 per cent in the brittle plants, comparison being made on the dry 
weight basis. When calculated on the wet weight basis, the ratio of crude fiber 
of the normal rye to the brittle is 13.04 to 3.81 per cent. The proportion of crude 
fiber on the wet weight basis is the proportion we would find in the stalk in the 
field, and this extreme difference in crude fiber may explain to a great extent the 
difference in the strength of the stems. 
The pentosan content of the brittle.rye is higher than that of the normal rye 
on the dry weight basis, but is almost the same on the wet weight basis. The 
pentosan material being chiefly hydrophilic colloids does not aid appreciably 
in the skeletal make-up or strength of the stalk, except as it enters into the compo¬ 
sition of the ligno celluloses. This higher percentage of pentosan in the brittle 
rye may explain the higher water content of the brittle stalks, when compared 
with the normal ones. 
