312 Introduction to Botany. 



new inflorescences arose in the axils of the fresh upper 

 leaves. 



In this instance, there is no special device to protect 

 the plant against the cold, and its power of resistance ap- 

 pears to be due solely to the character of the protoplasts. 



Another striking instance of the adaptation of the proto- 

 plasts to low temperatures is furnished by the small and 

 delicate alpine Soldanellas. These lie buried in the snow 

 during the winter ; but when the summer sun first melts 

 the upper layers of snow, and the percolating water 

 moistens the earth beneath, the flower buds of the Solda- 

 nellas begin to spring forth, although the earth and water 

 and the air filling the interstices of the snow must be near 

 the freezing point. As growth continues, a part of the 

 reserve materials stored in the prostrate leaves and subter- 

 ranean rootstock is used in the formation of new tissues, 

 and a part is united with oxygen in the process of respira- 

 tion, producing heat which melts the snow immediately 

 above the flower buds, thus enabling them to unfold above 

 the surface. Sometimes the buds blossom out while still 

 imprisoned beneath the snow (Fig. 163). 



196. Resistance to Heat. The plants of deserts and 

 regions of high temperatures show no modifications of form 

 which are directly adaptive to heat alone, but they are able 

 to withstand very high temperatures because of the nature 

 of their protoplasts. At Lahore and Multan, India, the 

 maximum temperatures are respectively 50.9 and 52.8 C. 

 (123.6 and 127 F.), and in the sun probably from 63 to 

 70 C. (145.4 to 158 F.); and the plants of those regions 

 have of course become adapted to these extremes. At 

 some places near the equator the soil temperature is known 

 to have risen to 80 C. (176 F.), and in one instance 

 even to 84 C. (183.2 F.). A species of Ipomoea has been 



