GO 



BLIGHT IN THE TEAR TREE. 



nical eflect, similar to that caused by gird- 

 ling or ringing a tree. This is, indeed, a 

 sufficient explanation of some few cases; 

 since it is undoubtedly true, that the effect 

 of the frozen and dead spot of bark, when 

 it extends quite round the tree, is exactly 

 similar to girdling it, or removing the same 

 quantity of bark altogether. The leaves 

 would expand in the spring, because the 

 upward current of sap would be carried on 

 through the young layer of wood of the 

 previous season. But when the current 

 commences passing downward through the 

 inner layer of bark, the tree must perish, 

 because the channel of communication is 

 cut off by the dead spot of bark. But sup- 

 posing, in this case, this spot to be on one of 

 the principal limbs, then the mortality would 

 be confined to the portion above this spot. 



But every one who has carefully watched 

 the frozen-sap blight, very well knows that 

 in these instances it is not confined to such 

 branch. On the contrary, in most cases, 

 if left to itself, it pervades the whole sys- 

 tem of the tree, the vitality of which is 

 destroyed. Sometimes its progress is so 

 rapid that the whole seems affected in a few 

 days ; at others, it is so gradual, that it is a 

 couple of years before the mortality is com- 

 plete. 



We have satisfied ourselves that this 

 effect is generally owing to the sap, which 

 is rendered poisonous to the tree by the 

 action of frost. 



Ijt. Because the malady is distinctly trac- 

 ed, in its early progress, by a discolouration 

 of the inner bark alone. It is through this 

 that the principal current of the sap is 

 carried on. That portion of the sap ves- 

 sels, ruptured and broken by sudden frost 

 and thawing, is more or less filled with 

 putrid decomposing vegetable matter. This 

 matter is taken up by the upward current of 

 sap, and disseminated through the branch 



above it, the adjoining parts, or through the 

 system of the tree. 



If the diseased part is large, and the poi- 

 sonous matter abundant, the tree will die 

 almost immediately on the commencement 

 of vegetation. But this is rarely the case. 

 The first upward current of the sap in the 

 spring, is so watery and abundant that it 

 would require to be very largely infected to 

 cause immediate death. In a few weeks, 

 however, as soon as the leaves have grown 

 large enough properly to elaborate the juices, 

 and the current of digested food sets down- 

 ward through the system of the tree, the effect 

 of the poison begins to show itself. If the 

 diseased spot is upon a branch, and is small 

 in extent, its effect will probably be con- 

 fined to the destruction of that portion. If 

 the portion is larger, but the diseased mat- 

 ter, or putrid sap, small in quantity, it may 

 only cause a general decline of health in 

 the tree. But when it is much extended, and 

 is once fairly taken up and distributed 

 throughout the system of the tree, nothing 

 will save it. If it does not all die the first 

 season, it will the second, or even, as we 

 have repeatedly observ^ed, two or three years 

 afterwards. When we can see, on raising 

 the inner bark, that it is discoloured, then 

 we may be sure the poison has already tra- 

 versed the sap vessels, and the fate of such 

 portion of the tree is sealed, however flou- 

 rishing it may yet appear in the outer bark 

 or the leaf, 



2d. Because the symptoms of the frozen- 

 sap blight are almost entirely similar to 

 those which are produced by inoculating the 

 system of a tree in early spring with a 

 small quantity of arsenic, or any other pow- 

 erful agent destructive to vegetable life. 

 If a little arsenic is introduced into the cir- 

 culation of a fruit tree at that season, it first 

 discolours the sap vessels of the inner bark; 

 then the leaves suddenly flag and droop; 



