TEMPERATURE AND LIGHT 229 



low valleys to the high mountains. Some of the algse grow in 

 hot springs, where the temperature approaches the boiling point, 

 while others grow in the arctic regions of perpetual snow. Some 

 plants are restricted to definite and limited regions by the tem- 

 perature, while others grow over a very wide range of territory 

 and under great variations of temperature. Some of these plants 

 attain considerable size under favorable temperate climates, but 

 are very small when grown in extremely low temperature. The 

 effects of temperature on vegetation can be readily seen when we 

 study the changes in vegetation as we ascend from the base to 

 the top of very high mountains. The distribution of many of our 

 agricultural crops is controlled largely by the temperature. 



Maximum, Optimum and Minimum Temperatures for Ger- 

 mination. These terms refer to the highest, most favorable and 

 lowest temperatures for germination and plant growth. These 

 temperatures are different for different species and are fre- 

 quently different for germination and growth in the same plant. 

 A few are given in the following tables : 



Temperature for Germination in C. Degrees. 



Plant Min Opt. Max. 



Corn 9.4 34 46.2 



Pumpkin 14.0 34 46.2 



Wheat ' 5.0 34 42.5 



Temperature of Growth in C. Degrees. 



Plant. Min. Opt. Max. 



Buckwheat 0-4.8 25-31 37-44 



Oats 0-4.8 25-31 31.37 



Wheat 0-4.8 25.31 31.27 



Peas 0-4.8 25-31 31-37 



Corn 4.8-10-5 37-44 44-50 



Pumpkin 10.6-15-6 37.44 44-50 



Cucumber . . 15.6-18-5 37.44 44-50 



