CHEMISTRY AND PHYSICS OF PLANTS, 87 
lowest or the highest. There are plants whose whole lives 
are passed in temperatures but little above the freezing 
point of water, the Red-snow plant being a good example. 
Many seaweeds flourish in waters which never rise above 
5° to 10° Cent. (40° to 50° Fahr.), while others grow only 
where the temperature is 20° to 30° Cent. (about 70° to 85° 
Fahr.). 
175. For ordinary land-plants the best temperature varies 
for the different parts and functions somewhat as in case 
of the lowest and highest. The best temperature for roots 
is generally somewhat lower than that for the parts above 
the ground, and likewise for the production of fruit and 
seeds it is higher than that for the simple growth of leaves 
and stems. 
176. The minimum, optimum, and maximum tempera- 
tures for the germination of the seeds of some common 
plants have been determined to be about as follows: 
Minimum. Optimum. Maximum. 
Indian Corn.) 9° C. (= 48° F.) |34°(C. = 92° F.) [46° C. (= 115° F.) 
Scarlet Bean.| 9° C. (= 48°F.) 34° (C. = 92° F.) |46°C. (= 115° F.) 
Pumpkin ...) 14°C. (= 56° F.) | 34°(C. = 92° F.) |46° 0. (= 115° F.) 
Wheat...... 5°C.(= 41°F.) |29°(C. = 88°F.) 42°C. (= 108° F.) 
Barley...... eo (=41°F.) |29°(C. = 88°F.) |87°C. (= 99° F) 
177. When the temperature rises above a certain point 
the death of the plant takes place. Those plants, or parts 
of plants, which contain the least water are capable of 
enduring higher temperatures than those which are more 
watery. The immediate cause of death appears to be the 
coagulation of the albuminoids of the protoplasm. The 
protoplasm thus loses its power of imbibing water, and 
the cells consequently lose their turgidity. In watery 
