FKEEZING. 469 



and coarse stones or brickbats. This furnishes me- 

 chanical support, and the tree may flourish as well 

 as before. 



6. Freezing — Congelatio. Plants vary in their 

 natural capability to endure frost. Late in the 

 autumn, and early in winter, the tree is not easily 

 stimulated ; and a severe frost, even after a warm 

 season, does not necessarily injure the tree. But 

 late in the winter, and early in the spring, when the 

 energies of the tree are active, a frost is very inju- 

 rious ; and if the buds are swollen, or the tree in 

 leaf, it is disastrous, possibly fatal ; because the tree 

 is then full of fluids, expanding as they freeze, and 

 the thin walls of the cells are thereby broken and 

 destroyed. When these thaw, the sap runs out 

 among the intercellular spaces, and deranges the 

 whole circulation. From the decomposition of the 

 stagnant sap it spreads decay through the whole plant. 



Duhamel and Buffbn maintain that frost-splits 

 occur more frequently — " Aux expositions du Nord 

 et du conchaut " — on exposures to the north than on 

 other aspects, because they were colder. On the 

 contrary, Ehrhart says : " Those trees or shrubs 

 planted on the southern side of the heights suffered 

 more than those on the north side." 



Dr. Caspary believed that these frost-clefts did not 

 depend upon cold winds coming in any one direction, 

 but upon injuries received, either from the decay of 

 40 



