400 MR. A. Je EWART ON ASSIMILATORY INHIBITION. 
metal covers during a period of severe frost, the range of tem- 
perature being taken by a differential thermometer, after 
exposure the plants being thawed and examined at 1° C. 
Leafy branches taken from the warm house (average tempera- 
ture 10? C. to 20° C.) were kept in a glass case surrounded by 
snow, examined at 1° C. and then brought to a temperature of 
15? C. (Table O). 
With tropical plants assimilation ceases to be perceptible at a 
temperature several degrees above zero (Table P). 
Experiments were also made with three-weeks old seedlings of 
certain plants developed under precisely similar conditions with 
regard to temperature (30° C.), exposure to light, amount of 
moisture, &c. 
TABLE Q. 
At —29 C. to —1? O. for 
1 day, and then examined 
at 1? C. 
3 days at —1° C. to 1° 0., 
then 1 day at —3° C. to 
— 5° C. 
Vicia Faba ; 
Helianthus annuus. 
Almost all leaves and leaf- 
cells living. At 1? C. at 
first no evol” of O, in 
4hr. at 20° C. moderately, 
and in 1-2 h. quite active 
evol? of O. 
Allleavesliving. Very faint 
evoln of O at 1° C. In 
l h. at 20? C. fairly, and 
in 2-3 h. quite active 
evol” of Oxygen. 
Ricinus communis ; 
All leaves living. At first 
Lupinus albus. 
no evol of O. In Lh. 
at 20? C. fairly, and in 2 
—3 h. quite active assim. 
At — 1? C. to 4-1? C. for 
1 day. 
Zea Mays ; 
Phaseolus vulgaris. 
Few leaves killed, rest show 
no evol” of O, none after 
2 h. at 209 C., weak in 
3 h., fairly active in 5 h., 
No evol” of O at 1? O., but 
assim. returns rapidly at 
209 C. and is normal in 
lhr. and allleaves remain 
normal in 1 day. living. 
The above table clearly shows that the most important factor in 
determining the resistant power of any given plant to cold is the 
hereditary nature and disposition of the plant itself, but how 
this acts and what the exact relation between the two may be is 
impossible to say. 
Though death caused by freezing is due to the withdrawal of 
water from the cell to form ice crystals, nevertheless resistance 
to desiccation and resistance to freezing are not necessarily 
