204 



EFFECTS OF FROST ON TREES. 



trary, it grows over and the tree continues 

 to prosper an indefinite period. Among fruit 

 trees I have witnessed this particularly in a 

 cherry tree, and every woodsman knows it to 

 be true of forest trees ; there being, in many 

 situations, but few great oaks, which on be- 

 ing sawed or split, do not show frost cracks. 

 Again the alburnum, chiefly the smaller 

 branches and one year's shoots, suffer prin- 

 cipally by freezing, where death is induced ; 

 and these from their more porous, softer 

 and tougher character, would bear mecha- 

 nical distension much better than the hard- 

 er and more brittle heart-wood, which rends 

 with the report of a cannon, forcing, it is 

 true, the thin covering of sap-wood on large 

 trees, (a) 



That the injury is chemical, seems to me 

 apparent from the fact, as you have well 

 observed, on frozen-sap blight, that the sap 

 is always discoloured, where freezing pro- 

 duces vegetable death ; and in fact the 

 whole substance of those parts of the tree 

 injured, immediately on thawing, show this 

 discoloration ; for example, if what we 

 usually call the roots of a tree, (or what 

 some botanists term underground branches,) 

 are exposed to an atmosphere below the 

 freezing point, it will be found that the ex- 

 tremities of the roots, taken from a consi- 

 derable depth, will perish from the slightest 

 freezing, while the upper portions, more 

 used to cold and less porous, will remain 

 uncolored and alive ; but if the freezing be 

 increased, the roots perish to the neck of 

 the tree, showing that the soft and porous 

 parts, least likely to be injured by simple 

 mechanical distention, is the first to yield up 

 vegetable life to the frost. 



Again, there is a striking resemblance 

 in the frozen and destroyed sap, to the ef- 

 fect produced by freezing on several kinds 

 of ink, dyes, etc., in which I presume no 

 one will doubt the injury is chemical. 



So too in the action of frost on the potato ; 

 its juices are evidently chemically vitiated, 

 not its substance mechanically destroyed ; 

 for even when grated, the potato will re- 

 tain its vitality for sometime in water, but 

 loses it instantly on being frozen and 

 thawed. Other vegetables, as the apple, 

 and turnip and beet, will bear more frost, 

 but intense freezing destroys most of them. 

 Nor does this destruction seem to depend 

 on the quantity of aqueous matter in the 

 vegetable, liable to distention by the frost ; 

 for the potato, the driest of the four vege- 

 tables named, yields its life to the least 

 freezing; and the beet less juicy than the 

 turnip or apple, next ; and the turnip stands 

 more than either. So it is with trees : one 

 variety, equally succulent, will bear more 

 frost than another ; as for example, the oak 

 will withstand more than the pear, and the 

 pear more than the tender exotic, which 

 demonstrates that it is not the quantity of 

 the water, but the definite composition of 

 the sap of each kind, that renders it more 

 or less liable to destruction by frost, and 

 proves that the destruction is not of the 

 woody vessels, which would readily yield 

 to the mechanical power of frost in all, 

 but to the chemical dissolution of the sap.(i) 

 The sap loses its proper character, as does 

 the ink, the dye, the potato, the beet ; and 

 instead of nourishing the tree, poisons, 

 and is as unfit for its use as is the potato, 

 after freezinsf, for the use of man. Indeed 

 the part of the tree undergoing this change 

 dies as suddenly as a man would, if the 

 whole blood of his system were converted 

 into hog-wash or swill. 



But it will be asked, if it is not the ex- 

 pansion of water by freezing, that bursts the 

 sap-vessels, why is it that it is always the 

 trees that are growing and succulent, or the 

 limbs that are in that condition, that are 

 destroyed by frost ? It is only trees in a 



