378 
Journal of Agricultural Research 
Vol. XXIII, No. 5 
either as a result of a summation of accidental errors or as a result of 
systematic errors in operation. 
Table IV shows the results obtained from nine different plantings of 
seed of four varieties, each figure being an average of three determina¬ 
tions. They were grown at different times and so represent effects of 
the small variations in temperature, moisture, or other environmental 
conditions in the incubators, which often were sufficient to cause a notice¬ 
able difference in the rate of growth of the seedlings. Of course, the 
handling of the samples from the time the plants were cut until the 
reaction of the juice was determined was made as uniform as possible. 
Table IV .—Range in the P H values, under the conditions of the experiments, of some 
wheat varieties resistant, and some susceptible, to stem rust 
Experiment No. 
Kan red 
(resistant). 
Turkey 
(susceptible). 
Khapli 
(resistant). 
Little Club 
(susceptible). 
6. 06 
6. 06 
5 - 92 
5 - 92 
6 . 02 
6 . oo 
5-99 
5. 86 
3 . 
6. 02 
6. oo 
6.oo 
5 - 9 i 
4 . 
6. 06 
5 - 96 
S- 94 
5 * 93 
5 . 
5-94 
6. 00 
S -96 
5-93 
6. oo 
5 * 95 
6.03 
5 - 98 
7 . 
5 - 99 
6.07 
6. 00 
5 ‘ 92 
8. 
5 * 94 
6. 04 
5 - 97 
5-90 
9 . 
6. oo 
5 - 97 
5-94 
5 - 92 
Average. 
6. oo±o. oio 
6. 01 ±0. 010 
5 - 97 ±0.008 
5. 92 ±0.007 
There is a difference of a little more than o. i P H between the extremes 
for each variety . 7 These are typical of the variations in the values 
obtained for any variety whether grown in the germinators or in the green¬ 
house. 
In order to determine whether minor differences in procedure during 
the handling of the sample played any part in producing the range of 
values reported in Table IV, or whether it was due solely to the slight 
changes in environmental conditions, four trays of Kharkov seedlings 
were grown in the same germinator at the same time, one above the other. 
On the seventh day these were expressed successively with the following: 
results: 6 
Sample No. 
Pb 
I. 
5. 922 
5 - 921 
5- 916 
5 * 921 
3. 
4. 
The close agreement between these values would seem to indicate that 
such differences as are recorded in Table IV are to be attributed to varia- 
7 These four varieties arc especially interesting from the standpoint of their resistance to stem-rust. So 
far as we know now, Khapliis very resistant to all biologic forms of this rust and Little Club is very suscep- 
bible to them all; Kan red is im mu n e from certain forms to which Turkey is very susceptible. According to 
Table I V, Little Club has a slightly greater hydrogen-ion concentration than the other varieties, the small 
probable errors of the averages making the difference seem significant. Whether this difference is constant 
for this variety when grown under incubator conditions was not determined, as too few seed lots were 
available. However that may be, it is clear that the averages show no correlation of acidity with rust 
resistance. 
