COLD AND GROWTH OF PLANTS COVILLE. 285 
growth had already begun to take place at the cold-storage tem- 
perature. The thermograph record for the 278 days was as follows : 
Hours. 
29° to 32° F 5,591 
32° to 33° 990 
33° to 34° 91 
The temperature record did not go above 34°. It is an astonish- 
ing fact that temperatures so very near freezing will start dormant 
l^lants into growth. 
On March 3, 1915, 58 cuttings from dormant outdoor blueberry 
plants w^ere placed in moist birch sawdust in commercial cold storage 
at 33° to 36° F. On December 4, nine months later, buds on every 
cutting had begim to grow. Not one of these cuttings gave a starch 
reaction when tested with iodine. The transformation of their 
stored starch into sugar was complete. (See pis. 8 and 9.) 
S. The theory advanced in explanation of the formation of sugar 
during the process of chilling is that the starch grains stored in the 
cells of the plant are at first separated by the living and active cell 
membranes from the enzyme that loould transform the starch into 
sugar, but lohen the plant is chilled the vital activity of the cell 
membrane is weakened so that the enzyme " leaks " through it, comes 
in contact loith the starch, and turns it into sugar. 
I have stated the theory in these words out of regard for simplicity 
and general understanding, but if anyone should require that it 
be presented in orthodox technical language it might be restated as 
follows. The reserve amylum carbohydrate bodies are isolated from 
the amylolytic enzyme by semipermeable protoplasmic living mem- 
branes of high osmotic efficiency, but under the influence of low 
temperatures the protoplasmic membranes are proximately devital- 
ized, they become permeable to the amylolytic enzyme, and amyloly- 
sis ensues. I may add, however, that the use of such terminology 
seems to me to involve a certain degree of unnecessary cruelty. 
From the evidence already presented no one, presumably, will 
question that the chilling of dormant trees and shrubs is followed 
by growth and that the growth is associated with the transformation 
of starch into sugar. But the hypothesis that this transformation 
is brought about by the weakening of the cell membrane and the 
consequent leakage of starch-transforming enzymes into the starch 
chambers may very properh^ be challenged. In the Tropics there 
is no chilling weather, yet trees and shrubs spring into growth 
after the dormant period of the dry season, just as they do in tem- 
perate climates after the dormant period of winter. The critical 
scientific man will therefore ask: Are there not other agencies than 
chilling which will start dormant trees and shrubs into growth even 
