No. 8. 



Canker in Pear Trees. 



261 



pit into a peach-house, and planted two old 

 peach and nectarine trees in it, both intole- 

 rably aflected with the canker and gum, 

 merely to furnish the trellises with a ?ew 

 fruit, until the young' trees should establish 

 themselves — in fact, I considered them as 

 castaways — but now, the middle of October, 

 the two old trees are furnished with most 

 beautiful bearing wood, without spot or blem- 

 ish : this has convinced me, that to cover the 

 most diseased tree with glass, would be to 

 cure the canker for ever. Now, I am aware 

 that it might be supposed that the removal of 

 those old trees caused them to produce that 

 short-jointed wood which is not so liable to 

 be attacked by the disease, but I have a pa- 

 tient out of doors which will answer for it- 

 self, and is worth a thousand theories. I re- 

 planted this tree at the time I planted those 

 in the house, and during the very favourable 

 spring of the present year, I was gratified to 

 see it make a beautiful start, but the sudden 

 change in the early part of June, from warm 

 weather to cold, gave a check to vegetation, 

 and my patient immediately showed signs of 

 disease. 



Tluis, it appears that a tree afflicted with 

 the canker is completely renovated by being 

 placed under glass ; and I am, therefore, of 

 the opinion, that a cold and unfriendly atmo- 

 sphere is the cause of the disease, its severity, 

 of course, aggravating its malignity very 

 considerably. 



Mr. Johnson asserts, that the disease com- 

 mences with an enlargement of the vessels 

 of the bark of a branch or of the stem, but I 

 conceive, that the enlargement of the bark 

 is not the commenceinent, but only an assu- 

 rance that the disease has already established 

 itself; and that it is not the returning sap- 

 vessels which are first diseased, but the con- 

 centric glands or pores, which are found in 

 the bark, that are first aftected by sudden 

 changes of the weather, and that from the 

 septic qualities of disorganised vegetable mat- 

 ter, decomposition or mortification com- 

 mences, which, thus disarranging the func- 

 tions of the returning sap-vessels^ causes the 

 enlargement; therefore I do not agree with 

 that gentleman, when he finds a resemblance 

 between the canker in trees, and any disease 

 in the animal system arising from indiges- 

 tion, &c., but would rather compare it with 

 those external diseases arising from too low 

 a temperature, where, the circulation being 

 stopped, speedy remedies must be resorted to 

 for restoration, or mortification will ensue. 



I have two apple tree:3, planted within 30 

 yards of each other, and both growing in the 

 same soil ; one of them is seriously afl^ected 

 with the canker, while the other is scarcely 

 affected with it — now how is it, that the one 

 is nearly destroyed by the disease, while the 



other is comparatively free from it 7 It is 

 thus — I prune my trees bowl-shaped, and 

 when these were young they bore a crop of 

 fruit which brought the branches of the can- 

 kered tree almost horizontal, and thus they 

 have remained; and it is these horizontal 

 branches which are nearly dead with canker, 

 from which I draw the following conclusions: 

 that as the scarcely-affected tree is in a shel- 

 tered situation, with its branches in an almost 

 perpendicular position, the north-east wind 

 had not cooled the bark below a given point ; 

 while the cankered tree, being in an exposed 

 situation, with its branches horizontal, its sys- 

 tem has been cooled below that given point, 

 and by that means its natural functions have 

 been checked. Pruning, no doubt, has a ten- 

 dency to prevent this disease, but as to Mr. 

 Johnson curing his russet apple tree of can- 

 ker by pruning, it is quite as probable that 

 milder seasons were the real doctor. Where- 

 ver a tree is planted, and whenever the whole 

 of its summer shoots are not ripened, it is 

 owing to its being either too tender a kind 

 for the situation, or the soil is ton good for 

 the climate, or the climate is a very bad one; 

 and when all these evils combine, it is not 

 surprising should the tree die of canker. 



In 1828 I had an apple tree of the first 

 quality fruit, but did not know its name; I 

 took an apple to Mr. Knight, who, as soon as 

 he saw it, pronounced it to be the " Golden 

 Harry," a most excellent apple in some situa- 

 tions; he said, "it is one I recommended to 

 Sir Joseph Banks many years ago; some 

 time after, as I was accompanying him round 

 his garden, he said, ' here is the Golden Harry 

 apple you sent me ; the tree has run wild, 

 and the fruit it bears is all cracked to pieces 

 and is worthless ; I shall send it to the rub- 

 bish heap.' So much for a good climate on 

 this apple," said Mr. Knight, " your garden 

 being an exposed one, just suits it." 



Formerly, it was the practice of writers on 

 the canker of fruit trees to blame the subsoil ; 

 but the subsoil of every situation varies as 

 much as the surface soil; and while one 

 blames the cold clay and another the sand, 

 and the prevention of these roots from pene- 

 trating these subsoils seems to be the pana- 

 cea for all the cankering evils of these vari- 

 ous situations, is it not singular, that the 

 cankering matter should be found in every 

 snbsoil with a north-east exposure"? The 

 mystery is solved at once, when we consider 

 the withering and penetrating power of the 

 weather upon spongy and unripened wood. 

 The disease may proceed also from bruises 

 and the attack of insects; but all these pro- 

 duce insignificant effects, compared with those 

 of an inclement atmosphere." 



Will our correspondent examine carefully his situa- 

 tion, as well as subsoil, and ascertain whether the evi] 



