172 
Journal of Agricultural Research voi. xxviii, No. 2 
Table IV .—Thickness of the cell wall in brittle and normal rye 
Brittle 
rye 
Normal 
rye 
Epidermis: 
External wall. 
Microns 
2 .4-2.9 
Microns 
5.3 
Side wall.... 
.9 
3.3 
9.6 
4.8 
Sclerenchyma. 
2.8 
Vascular bundle: 
Sheath. 
.4-1.9 
Pitted vessel. 
1.4 
2.4 
Spiral vessel.:. 
3.2-4.8 
4.8 
Pith cell. 
.4- .9 
2.4 
The data recorded in this table corresponds well with the chemical estima¬ 
tion of crude fiber. Besides thickness of wall, the size of the cells is a factor de¬ 
termining the proportion of crude fiber. 
Microchemical examination, using phioroglucin — HCl, showed lignin through¬ 
out the walls of both brittle and normal rye, except in the phloem and xylem 
parenchyma of the fibro-vascular bundles. Differences were in degree rather 
than in extent of lignification. It was not found practicable to attempt to 
distinguish between pentosans in the wall and the protoplast, because pentoses 
demonstrated in the vacuole could easily have diffused in from the hydrolized 
pentosans of the wall. 
SUMMARY 
Brittleness of straw, chlorophyll deficiency, male sterility, and crinkled awns 
were found as abnormalities in inbred strains of Minnesota No. 2 rye. 
Chemical analyses show a low percentage of crude fiber (14 per cent) and 
high pentosan (34 per cent) content in brittle straw compared with a crude 
fiber content of 32 per cent and pentosan content of 25 per cent on a dry- 
weight basis in healthy rye plants. Brittle plants have a high moisture con¬ 
tent correlated with high pentosan content. The differences in starch, pectin, 
ash, and sugar content of normal and brittle rye plants are not gyeat in amount. 
Evidently the carbohydrates in the brittle plants are not normally trans¬ 
formed into cellulose and wall-forming substances designated as crude fiber, 
but accumulate as pentosans. 
The greater thickness of cell wall in the normal rye accounts in part for its 
greater strength as compared with brittle rye straw. 
The amount of lignin in normal rye straw greatly exceeds that in brittle rye 
