CBEMISTBT AND PllTSIGS 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: 



MnnunM. 



Optimdm. 



MAxiunn. 



Indian Corn. 

 Scarlet Bean. 

 Pampkin . . . 



Wheat 



Barley 



9° 0. (= 48° F.) 

 9° 0. (= 48° F.) 

 14° C. (= .56° F.) 

 5°C. (=41°F.) 

 5°C. (=41°P.) 



34° (0. -93°F.) 

 84° (C. = 93° F.) 

 34° (C. = 93° F.) 

 39°(C. = 88°F.) 

 39° (C. = 83° F.) 



46°C. (=115°P.) 

 46° C. {= 115° F.) 

 46° C. (= 115° F.) 

 42° 0. (= 108° F.) 

 37°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 



