Plants as Affected by Cold. 121 



water or covering with snow. They should be handled as little 

 and as carefully as possible while frozen. Sprinkling with 

 cold water is often sufficient to restore frost-bitten plants. 

 Aside from the death of tender plants by cold, more 

 or less hardy species suffer injury in a variety of ways, 

 of which the following are examples: 



192. Destruction of Terminal Buds by Cold. In plants 

 which do not mature their terminal buds, in autumn, as 

 the raspberry, sumac, grape etc., destruction of the tips 

 of growing shoots by frost is a regular occurrence in 

 climates of severe winters. The distance which the 

 shoots are killed back depends upon the succulency of 

 the growth, the severity of the winter and the natural 

 power of the plant to endure cold. Plants thus affected 

 are not always to be regarded as tender, since they often 

 grow wild in climates of very severe winters. 



193. The Darkening of the Wood (black-heart) of certain 

 trees, as the pear, in climates of severe winters, appears 

 to be a chemical effect of the cold. It begins at the cen- 

 ter of the stem and in extreme cases may extend clear to 

 the cambium, when the bark ceases to adhere, and the 

 tree or branch thus affected dies. In stone fruits, this 

 trouble is often accompanied by a flow of gum. If the 

 coloring of the wood does not extend to the cambium, 

 the tree or branch may survive, but the first season 7 s 

 growth thereafter is generally feeble and the fruit or the 

 seed crop often fails. Daring the second season, healthy 

 growth may be resumed, but the heart- wood is rarely or 

 never restored to its normal color. Black-heart often 

 results from other causes than cold, as from bacteria that 

 gain access to the heart- wood through wounds (418). 



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