SOIL, SITUATION AND ASPECT. 49 



rature upon vegetation. These are stated "by M. De 

 Candolle, as follows : 



1. All other things being equal, the power of each 

 plant and of each part of a plant, to -resist extremes 

 of temperature is in the inverse ratio of the quan- 

 tity of water thej contain. 



2. The power of plants to resist extremes of tem- 

 perature is directly in proportion to the viscidity of 

 their fluids. 



3. The power of plants to resist cold is in the 

 inverse ratio of the rapidity with which their fluids 

 circulate. 



4. The liability to freeze, of the fluids contained in 

 plants, is greater in proportion to the size of the cells. 



5. The power of plants to resist extremes of tem- 

 perature is in a direct proportion to the quantity of 

 confined air which the structure of their organs give 

 them the means of retaining in the more delicate 

 parts. 



6. The power of plants to resist extremes of tem- 

 perature is in direct proportion to the capability 

 which the roots possess of absorbing sap less exposed 

 to the external influence of the atmosphere and the 

 sun. 



From this it will be obvious that all rank growth 

 and succulent vegetation should be avoided where 

 the desired object is to obtain hardy vines. 



