COPPER SPRAYS ON IRISH POTATO TUBERS. 9 
The proportion of solids in most cases showed a gradual increase 
during the growth of the tubers. With the exception of the Green 
Mountain sample, the proportion of solids was higher in the tubers 
from copper-sprayed plants than in those from the unsprayed plants 
at the time of the first analysis, that is, when the tubers were less 
than an inch in diameter. This indicates that the effect of the copper 
was exerted very early in their development. 
The solids for all the tubers from the Bordeaux-sprayed plants 
averaged 18.63 per cent; for all those from the unsprayed plants, 
17.87 per cent; for all those from barium-water-sprayed plants, 19.58 
per cent; and for all those from Pickering-sprayed plants, 18.29 per 
cent. 
The following average ash figures were obtained for all the samples 
analyzed: Tubers from unsprayed vines, 0.87 per cent; tubers from 
Bordeaux-sprayed plants, 0.88 per cent; and tubers from Pickering- 
sprayed plants, 0.85 per cent. The percentage of the total ash found 
as insoluble ash decreased in most cases during the growth of the 
tubers. 
The pH data obtained on the water extracts of the tubers showed 
no significant change. 
The proportion of total nitrogen, which increased during the 
growth of all four varieties of tubers, was somewhat higher for the 
tubers from copper-sprayed plants than for those from the un- 
sprayed plants. The percentage of nitrogen was higher for the 
tubers from copper-sprayed plants than for those from the unsprayed 
plants at the time of the first analyses, showing again that the action 
of the copper on the metabolic activities of the plant was exerted 
very early. 
The percentage of insoluble nitrogen in the tubers showed a tend- 
ency to decrease during growth. The percentage of soluble nitrogen 
increased during growth. The percentage of coagulable nitrogen 
increased during growth-in the case of the Irish Cobbler, the Early 
Ohio, and the Early Rose varieties, but not in the Green Mountain 
variety. The monoamino and amid nitrogen, which includes the 
nitrogen not precipitated by phosphotungstic acid, showed a marked 
increase for all four varieties during growth. The average per- 
centage was slightly higher in the tubers from copper-sprayed plants 
than in those from the unsprayed plants. The ammonia nitrogen 
content showed no regular change. | 
During tuber development the percentage of starch increased some- 
what more rapidly than the percentage of solids. A larger percent- 
age of starch was usually found in the tubers from copper-sprayed 
plants from the first analysis to the last than in the check tubers. 
The average data for the content of starch in the tubers were: Bor- 
deaux-sprayed, 12.24 per cent; check, 11.73 per cent; barium-sprayed, 
12.67 per cent; and Pickering-sprayed, 12.36 per cent. 
The sugars,,.calculated as dextrose and sucrose, were present in the 
young tubers in relatively large proportions. At the time the tubers 
had reached maturity the dextrose had practically disappeared and 
the quantity of sucrose had markedly decreased. The unsprayed 
tubers of the three early varieties contained a higher percentage of 
sugars in the first stages of development and usually a lower per- 
centage at maturity than the tubers from copper-sprayed plants. 
27475 °—23——_2 
