Decline of Growth and the Rest Period. 107 
plants, the ability of the plant to endure these extremes de- 
pends upon the extent to which the protoplasm becomes 
dormant during the decline of growth. Asa rule, a given 
plant is hardy (10) in a locality in which the duration and 
warmth of the growing season are sufficient to complete and 
fully mature its normal amount of growth. Varieties of 
the apple, and other trees, that so far complete their growth, 
in any given locality, that their leaves fall before hard 
frosts, are rarely injured in winter, while those that continue 
growth until their foliage is destroyed by freezing suffer in 
severe winters. Deciduous trees in a climate where none of 
the leaves fall before hard frosts, as is the case with the 
peach, apricot and nectarine in the northern United States, 
must be regarded as tender and liable to destruction in 
severe winters. 
176. Individual Plants Cannot Adjust Themselves 
to a New Environment except to a slight extent. The 
power to complete the annual growth processes and become 
sufficiently dormant to endure the rigor of the rest period, 
in any given locality, is inherited, and not acquired. We 
are, therefore, able to do very little toward inuring or aceli- 
matizing (ac-cli’-ma-tiz-ing) individual plants to an environ- 
ment to which they were not adapted by nature. We may, 
however, through the variations of offspring (18), secure 
varieties that can endure an environment that the parents 
could not endure. 
177. Plant Processes during the Rest Period may not 
entirely cease. Although assimilation is wholly suspended, 
root growth and the callusing (73) of injured root surfaces 
proceed to some extent during the winter, in unfrozen 
layers of soil; and in sufficiently mild weather, the reserve 
