58 
ELEMENTS OF AGRICULTURE. 
97. Vegetation in general suffers from intense cold, but 
more particularly that of certain plants. But what does 
the most injury, in these cases, are the sudden changes in 
temperature ; and the damage is greater to plants growing 
upon light soils. Whenever the temperature falls gradu¬ 
ally, vegetation suffers but little. It is for this reason that 
a frozen plant should never be put in a warm place. To 
restore its vigor, we should give it a temperature that will 
cause it to thaw insensibly. 
98. It is particularly after great moisture that plants 
suffer when overtaken by frost; for in this case the stem 
is more tender and watery. The water and sap, that are 
increased in volume by congelation, then burst the tissues 
of the plant, and destroy the vital principle of certain in¬ 
dispensable organs. 
QUESTIONS. 
1. What is. the climate of a country ? 
2. What are the principal climates ? 
3. Are there others? 
4. Does the position of a place influence its climate? 
5. Can the same plants be cultivated in places of different temperature t 
6. -In which climate is vegetation most rapid ? 
7. Is vegetation injured by cold 1 
8. When is a change of temperature most hurtful ? 
9. How must we proceed to thaw a plant ? 
10. In what circumstances do plants suffer most from cold ? 
LESSON XI V. 
T~ ^ EFFECT OF CLIMATE UPON CULTIVATION AND UPON 
ANIMAL ECONOMY. 
99. In the preceding lesson, we indicated the causes 
upon which the state of a climate depends, and its general 
effects upon vegetation. We have yet to consider it undei 
