TEMPERATURE, LIGHT, AND MOISTURE 119 



as they are means of avoiding the injuries likely to be caused 

 by sudden changes of temperature. On the other hand, the 

 dark colors of bud scales readily absorb heat in sunshine and 



F 



FIG. 87. Epidermal hairs and scales. (Much enlarged) 



A, mullein; B, geranium; C, deutzia; D, hollyhock ; E, dame's violet; 

 F, shepherd ia 



may thus increase the temperature of the buds during the 

 cool days of early spring. 



Artificial protection from the cold. Snow is of such great 

 value as a protection of plants in winter that it is frequently 

 called " the poor man's manure." Winters in which there is 

 little snow are very trying to plants because they are left un- 

 protected and are thus easily heaved by the frost. Man often 

 adds to the natural protection of plants by mulching, shading, 



