130 MISSOURI BOTANICAL GARDEN. 
The greatest freezing point lowering, 2.03°C., and the 
least freezing point lowering, 0.596°C., constitute but a 
small range in temperature. Nevertheless, within this range 
there occur several similarities of conduct under varying 
conditions, to which it may be well to call attention here. 
Viburnum Opulus sterilis, collected and frozen on separate 
days from different plants, vary but 0.116°C. from each 
other. However, in Aesculus austrina, collected in the sun, 
and that collected in the shade at the same time and 
from the same tree, there is a difference of 0.155°C., the 
lowest freezing point lowering being for the sample from 
sunlight. The maximum lowering of 1.2985°C., and the 
minimum of 0.741°C., for Magnolia cordata and Magnolia 
_Lennet X respectively, indicates a wide difference in the 
behavior of this group. Their relations from the foregoing 
table are here submitted for more graphic comparison :— 
1910 OBSERVATIONS. 1911 Freezing TESTs. 
obovata purpurea grandiflora 
obovata purpurea 
glauca 
stellata M. cordata 
Kobus M. stellata 
cordata ‘M. Soulangeana 
Soulangeana M. obovata discolor 
obovata discolor M. Kobus 
M. 
M 
M 
M 
+ acuminata 
M. Umbrella 
Yulan M. Yulan 
grandiflora nll Lennei X 
SPERERREE REE 
7m 
E 
2 
Taking the observations of 1911 as a basis, there would 
seem to be a very close relation between the behavior of 
this group in actual and artificial conditions. With the 
exception of Magnolia grandiflora and, perhaps, of Magnolia 
Kobus, the lines connecting the members of the two groups 
diverge but little. The impression seems to be given that 
within species of the same genus, differences in the density 
of the cell sap result in differences in the resistance of 
the plants to freezing weather, and the relative relation of 
the species in this respect may be determined by a knowledge 
of the freezing points of their cell saps, obtained under 
