B. F. LUTMAN 
plant's energy would then be tending upward toward flower and seed; 
but tuber production in the high-bred specialized plant begins immediately, 
and the acquired tendency is for this process to claim the major part of the 
food. 
''As a result of this conflict of tendencies in the plant there occurs a 
critical period during which the continued health of the plant, if not its very 
life, hangs in the balance. 
''Whether this explanation is correct or not, the fact is certain that the 
fortnight including and immediately following the blossoming period is the 
turning point, the crisis in the hfe of the potato plant." 
The soil of the region around Burlington, Vermont, is in the main a 
light sandy loam. On this soil tip-burn, which is the external evi|dence of 
the crisis through which the plant passes, is severe. No better location, 
therefore, could be found for making observations on the internal factors, 
chemical and physical, that are at play inside the potato plant during the 
growing season. However, the crisis mentioned by Jones is more than a 
fortnight long; it lasts at least a month or six weeks, as the observations 
made during the course of the present work will show. 
The osmotic pressures in the plant are the result of the presence of sugars 
or inorganic salts in solution in the cell sap. So far as could be ascertained 
no analysis of the sap itself was available, but the ash of the plant has been 
investigated a number of times. 
Choslowski (3) found considerable percentages of glucoses early in the 
season both in the pith and in the vascular portions of the potato stalk. 
After June 28 only the pith contained glucoses. After August 26, two weeks 
before the death of the plants, the percentage of sugars in the stems had 
diminished. The young tubers and their stolons were very rich in glucose 
early in the season, but after June 28 showed little sugar. He attempts no 
explanation as to their movement other than to state that they move in a 
diosmotic manner. 
Kellermann (12) determined that the calcium, potassium, and phos- 
phorus in the ash of potato leaves and stalks increased to a certain maximum 
during the summer and then rapidly fell away during the last few weeks of 
growth. 
Seissl and Gross (15, 16) found that the potato leaf ash contained a 
maximum of P2O5 and K2O on July i and that the percentages decreased 
from that date until the harvest, October 10. The same investigators also 
found generally a maximum percentage of CaO, MgO, K2O, SO3, and P2O5 
in the leaf ash on either July i or August i, with a decrease after the latter 
date. A few exceptions to this rule can be found in their tables of analyses, 
but these are due to specific fertilizer applications. The late summer and 
autumnal decreases in CaO, MgO, SO3, and P2O5 percentages were espe- 
cially marked with the Johannis, while the decrease in P2O5 content was 
notable in both Johannis and Perkun, whatever the fertilization. 
