402 
Journal of Agricultural Research voi. xxvn, no. 6 
used: Seedlings of the different varieties were frozen in carbon dioxid 
and pulverized while still frozen. The powdered plant tissue was thawed 
at room temperature and the sap then extracted by pressure. Freez¬ 
ing-point depression was determined by means of a Beckmann ther¬ 
mometer. Total solids and average molecular weight of solutes were 
determined by the refractometric method described by Gortner and 
Hoffman ( 18) . A Leeds and Northrup type (K) potentiometer was 
used in securing the hydrogen-ion values. The results of these de¬ 
terminations are given in Table X. For analysis of sugars present in 
the sap, seedlings were grown under continuous light. 4 Samples of 25 
gm. each, green weight, were extracted in methyl alcohol, and total 
and reducing sugars determined by the picric acid method described by 
Rose (45). Dry weight was determined from separate samples dried at 
65° in vacuum. The results of sugar determinations are given in Table 
XI. 
Table: X .—Physicochemical properties of the sap of six wheat varieties 
Wheat variety. 
Ereezing- 
point de¬ 
pression. 
Refracto¬ 
metric 
solids. 
Average 
molecular 
weight of 
solutes. 
Ph. 
Relative 
suscepti¬ 
bility. 0 
Khapli, C. I. 4013. 
Mindum, C. I. 5296. 
°C. 
°- 95 
0. 98 
0. 91 
1. 08 
1. 02 
0. 82 
8. 50 
173 
5 - 984 
6.194 
6. 062 
5.890 
5 - 973 
3-899 
2. 2 
41. 2 
40. I 
32. 8 
60.8 
88.4 
Kota, C. I. 5878....... 
Kanred, C. I. 5146. 
Marquis, C. I. 3641.. 
Little Club, C. I. 4066. 
7 - 55 
8. 40 
7. 00 
6. 46 
177 
1 59 
*38 
155 
« 100=completely susceptible. Unpublished computations of E. C. Stakxnan and M. N. Levine on the 
basis of reaction of wheat varieties to all known biologic forms of P. graminis triiici. Little Club, while 
susceptible to all biologic forms, does not always produce the most virulent type of infection. 
Table XI .—Determination of sugars in sap of six wheat varieties 
Wheat variety. 
Reducing. 
i 
As sucrose. j Total. 
Percent¬ 
age of 
green 
weight. 
Percent¬ 
age of 
dry 
weight. 
Percent¬ 
age of 
green 
weight. 
Percent¬ 
age of 
dry 
weight. 
: 
Percent¬ 
age of 
green 
weight. 
Percent¬ 
age of 
dry 
weight. 
Khapli, C. I. 4013. 
Mindum, C. I. 5296. 
Kota, C. I. 5878. 
Kanred, C. I. 5146. 
Marquis, C. I. 3641. 
Little Club, C. I. 4066. 
O. 6856 
.6857 
. 7680 
• 8531 
• 7515 
• 73 I 5 
7.4072 
7.3896 
8. 3296 
8. 9392 
8. 0992 
8. 6544 
O. 1420 
.2376 
. 0809 
. OOOO 
. OOOO 
. OOOO 
1.5176 
2. 57°4 
o- S 3 12 
0. OOOO 
0. OOOO 
0. OOOO 
O. 8276 
.9242 
. 8489 
•8531 
•7515 
• 73*5 
8. 9248 
9. 9600 
8. 8602 
8- 939 2 
8. 099 
8. 654 
Table X shows that there are some differences in the physicochemical 
properties of different wheat varieties. There is a smaller percentage of 
solid matter in the sap of Little Club than in that of the other varieties. 
This is indicated both by the freezing-point determination and refracto¬ 
metric methods. There appears to be no correlation, however, between 
4 The plants were grown in one of the constant-light rooms described by Harvey ( 21 ). 
