646 THE PEAR. 



The remedy for the insect Wight is veiy distinct. It is that origin all j^ 

 suggested by Mr. Lowell, which we and many others have pursued with 

 entire success, when the other form of the disease was not also present. 

 The remedy consists, at the very first indications of the existence of the 

 enemy, in cutting otf and burning the diseased branch, a foot below the 

 lowest mark of discoloration. The insect is tisually to be found at the 

 bottom of this blackened point, and it is very important that the 

 branches be removed early, as the Scolyttis is now about emerging from 

 his burrow, and will speedily escape us, to multiply his mischief else- 

 where. If there is mtich appearance of the insect blight, the tree 

 should be examined every noon, so long as there are any indications of 

 disease, and the amputated branches carried at once to the fire. 



2. The Frozen-sap Blight. We give this term to the most for- 

 midable phase of this disease that aflects the pear-tree. Though it is by 

 ordinaiy observers often confounded in its aftects with the insect 

 blight, yet it has strongly characteristic marks, and is far more fatal in 

 its eftects. 



The symptoms of the frozen-sap blight are the following : First. 

 The appearance, at the season of winter or spring pruning, of a thick 

 clammy sap, of a sticky nattire, which exudes from the wounds made 

 by the knife ; the ordinary cut showing a clean and smooth surface. 



Second. The appearance in the sj)ring, on the bark of the trunk or 

 branches, often a considerable distance from the extremities, of black, 

 shrivelled, dead patches of bark. 



Third. In early summer months the disease fully manifests itself 

 by the extremities shrivelling, turning black, and decaying, as if sitd- 

 denly killed. If these diseased parts are cut off, the inner bark and 

 'heart-wood will be found dark and discolored sotae distance below 

 whei'e it is fresh and green outside. If the tree is slightly affected 

 only, it may pass off with the loss of a few bi-anches ; but if it has been 

 seriously tainted, the disease, if not arrested, may, sooner or later, be 

 carried through the whole system of the tree, which 'v\t.11 gradually de- 

 cline or entirely perish. 



To explain the nature of this disease we must first premise that, in 

 every tree, there are two citrrents of sap carried on : 1st, the tipwaj'd 

 current of sap, which rises through the outer wood (or alhurnum), to 

 be digested by the leaves ; 2d, the downward current, Avhich descends 

 through the inner bark (or liber) ^ forming a de])()sit of new wood on its 

 passage down.* 



Now let us su})pose, anterior to a blight season, a very sudden and 

 early winter succeeding a damp and warm atttumn.f The summer having 

 been dry, the growth of trees was completed early, but this excess of 

 dampness in autumn forces the trees into a vigorovis second gi-o^~th, 

 which continues late. While the sap-vessels are still filled with their 

 fluids, a sharp and sudden freezing takes place, or is, perhaps, repeated 

 several times, followed, in the daytime, by bright stm. The descend- 

 ing current of sap becomes thick and clammy, so as to descend with 



^ Being distributed towards the centre of the stem by the medullary i-aya 

 which communicate from the, inner bark to the pith. 



f Which always happens previously to a summer Avhen the blight is very 

 prevalent, and will be remembered by all as having been esiiecially the 

 case in the autumn of 1843, which preceded the extensive blight of the next 

 season. 



