Materials in Evergreen Herbaceous Leaves. 207 
Table IV. 
Material containing Starch exposed to extremely low Temperature. 
Dale • Temperature. Experiment. Control. 
Dec. 13 4°F. (— i5°C.') Strong starch reaction Strong starch reaction 
,, 20 — i6°F. (— 26° C/) No decrease in starch, cells ,, ,, 
strongly 
„ 23 - I9°F. (- 28 c C.) 
From Tables III and IV it is 
amount of starch undergoes re- 
conversion, in which the starch 
is changed back into oils and fats 
if subjected to moderately low 
temperature. If, however, the 
material, full of starch and hence 
in a summer condition, is subjected 
to extremely low temperatures no 
reconversion takes place and the 
material is killed. The strong 
plasmolysis of the cell contents 
exhibited in this material is shown 
in Fig. 7. 
plasmolysed 
?> >> >> 
seen that material containing a large 
Fig. 7. Cross-section of Linnaea leaf. Material 
outside for reconversion during extremely low tem- 
perature. Section treated with iodine solution. 
Starch grains visible in epidermic cells. Owing to 
the high starch content, the plasmolysed cell con- 
tents were stained deep blue. 
IV. Cause of Conversion. 
The conversion of fats to starch is quite impossible as an unaided 
chemical change, and hence the action of an enzyme is suggested. Tests 
were made for the presence of an enzyme both in material fresh from out- 
side and in that which had been exposed to higher temperature for some time. 
The test in this case was an alcoholic solution of guaiacum resin, which, 
with the addition of hydrogen peroxide, gives a blue reaction in the pre- 
sence of any enzyme. In enzyme tests made December 7 and 18 in fresh 
material no reaction was obtained. Material, however, which had been 
exposed to higher temperature for several days gave a strong reaction when 
tested. 
About a month later (Jan. 11-id) material in the same condition was 
tested which yielded rather different results. In the interval, however, the 
weather had moderated and some very high temperatures had been recorded. 
All Linnaea leaves, both from outside and inside, then responded very 
strongly to the enzyme test. There was an inclination at first to doubt the 
test, but when leaves of Begonia and Geranium from a greenhouse gave 
negative results it was concluded that the change in temperature must have 
affected the outside material. Still the change had not been great enough to 
