LIGHT AND HEAT 75 



Its protoplasm must be made of sterner stuff than most 

 plants. 



Acclimatization of Plants. Southern races habituated 

 to warm conditions are very susceptible to cold, and not 

 easily cultivated in cold countries, except in warm green- 

 houses. Some plants, however, may, if suitable measures 

 be taken, be gradually acclimatized. During the winter 

 they are kept in the greenhouse ; in the spring they are 

 not put out in the open at once, but are first transferred 

 to a cooler house or frame till they are hardened off. 

 In this way they are gradually inured to colder conditions 

 before being bedded out. 



