CHAPTER X. 



THE EFFECT OF FROST ON PLANTS. 



qpHIS is a matter of such moment that it needs 

 Oi to be closely studied, and, if possible, thoroughly 

 understood by all persons engaged in agricultural 

 or horticultural pursuits. Either extreme of heat 

 or cold is damaging to vegetation. Some plants 

 are hardier than others, and so are less easily affect- 

 ed by either extreme. Some families of plants are 

 so hardy that they extend over nearly the habitable 

 part of our globe. Some perennials are created 

 with reference to greater heat, and are so limited Th 

 their natural condition to the tropics or the torric! 

 zone. Others are created with reference to extreme 

 cold, and hence are found in Arctic regions or on 

 lofty mountains. While others, annuals, reach 

 maturity within a few months, in order that their 

 growth may be extended over a wider area of earth. 

 These live in cold climates only during the warm 

 months. Some plants are limited to a very narrow 

 belt Humboldt gives the natural limit of the or- 

 ange from 12 to 40 north latitude. Of course 

 the orange can survive in this higher latitude only 

 where the climate is affected by warm ocean cur- 

 rents. 



