May, 1922] RAINES — VEGETATIVE VIGOR OF THE HOST 
217 
Barley 
Date 
Sown 
Observations 
No. of Days 
to Head 
July 8 
July 17 
July 24 
Aug. 12 
Aug. 26 
Sept. 15 
Oct. I 
Oct. 23 
June 10. . . 
June 23. . . 
July 6.... 
July 20. . . 
Aug. 5-. -. 
Aug. 25. . . 
8" 
4" 
15" 
15" 
3" 
H 
18" 
8" 
H 
15" 
9" 
H 
15" 
6" 
2 
I 
20" 
10" 
6" 
I 
3 
I 
H 
15" 
10" 
I 
15" 
12" 
44 
50 
50 
70 
third leaf. The rust increased steadily in abundance on the leaf blade 
until it reached the maximum, and only then began to appear on the leaf 
sheaths. On the stem there were never more than a few scattered pustules. 
Teleutosori did not appear until the middle of September. They were to 
be found only on plants of the two oldest plots, and then not without care- 
ful search. The observations of October 23 showed a distinct drop in the 
amount of rust on all the plots of wheat. The new leaf growth of October 
tended to show but little rust. In view of Johnson's (1912) findings that 
low temperatures promote uredospore germination, these observations 
may be interpreted as indicating greater resistance to rust infection on the 
part of the host tissue due to the decreased rate of metabolic activity con- 
sequent on the onset of cooler weather. 
All of the plots of rye except that sown August 25 headed out, but the 
rate of growth varied as is indicated by the successively greater intervals 
required by the ^^ounger stands to head out. The behavior of the rust on 
the plots of rye was much the same as on the wheat. In the younger 
plantings it was somewhat less marked and less severe than on the wheat 
plants of the same age, but the development of the rust was more severe 
on the rye than on the wheat. It seemed, too, to go more readily to the 
leaf sheaths and stems in the case of the rye. No teleuto was found on 
the rye. 
Of the oats, the first three plots headed out in 77, 65, and 70 days 
respectively; the fourth plot produced only one head, 91 days after planting. 
The plots planted August 5 and August 25 never headed out. No rust 
appeared on the oats until August 12 when four plots were up, ranging in 
age from seedlings in the four-leaf stage to plants in bloom. The rust 
appeared on all four of the plots at the same time and in relatively the 
same abundance. However, once the rust had appeared, its subsequent 
history on the various plots differed decidedly. The older the plant, the 
greater the abundance of rust on it, and the larger proportion of the rust 
in the teleuto stage. 
In the series of barleys, the three older plots headed in 42, 50, and 50 
days respectively. The fourth put out a few heads 70 days after planting. 
