102 MISSOURI BOTANICAL GARDEN. 
final result. Can we then narrow our argument down to 
the ability of the cell sap to resist freezing? 
In the latter part of April, 1910, there occurred through- 
out the State of Missouri, a drop in temperature to 25°F. 
Foliar growth of the trees and shrubs was in an advanced 
condition, and the freeze, which was accompanied by rain 
and snow, did a great deal of damage to all green material, 
but, as is the case generally, destroyed the foliage of some 
trees and shrubs more than of others. As a matter of per- 
sonal interest, the damage to foliage was recorded in detail, 
and these notes occur in this paper as Table 1. From these 
observations alone, no conclusions as to the reason for the 
difference in resistance to freezing were apparent. Many 
plants which would reasonably have been expected to behave 
the same, acted quite differently, and the problem became 
more perplexing the more it was studied. 
A year later, 7. ¢., in the spring of 1911, it was decided 
to extract the saps of the various leaves, freeze them arti- 
ficially, and determine their freezing points, thereby ascer- 
taining if any correlation existed between this artificial 
behavior and that actually exhibited in the freeze of the 
year before. These results and conclusions are the basis 
of this paper. Only trees and shrubs growing in the Mis- 
souri Botanical Garden, out of doors, were observed, and 
their native habitats, fide Index Kewensis, are given in 
Table 1. As a matter of convenience it has seemed advis- 
able to separate the results of natural from artificial freez- 
ing, the two being essentially different investigations, and 
to summarize in the conclusion such correlations as may 
occur. 
The paper then comprises :— 
1. Notes on the effect of the freeze of April 24, 1910, 
on the trees and shrubs growing in the Missouri Botanical 
Garden, their recovery and other data. 
2. The freezing point of leaf saps, determined arti- 
ficially, and notes in connection therewith. 
3. Conclusions. 
