2? 



ON THE CAUSE OF CANKER IN APPLE TREES. 



BY D. CAMERON, A.L.S. 

 (Continued from p. 9.) 



The best, and indeed the only remedy for Canker, is carefully to drain the 

 ground where the trees are planted, so as to make the soil drier and warmer, 

 by which means the trees send out their roots at an earlier period. It would 

 also be advantageous to plant the trees on a raised mound. In such situations 

 they ought also to be kept thin of wood by pruning, so that the roots may have 

 fewer branches to support. Another cause of canker, even in favoured situations, 

 upon a dry and warm bottom, sometimes arises from severe late frosts, after the 

 sap is in motion ; when the sudden transition from a cold frosty night, to the 

 clear sunshine of the following day, often causes a bursting of the rind, in some 

 parts of the trees. Such injured portions should be immediately cut out, in order 

 to prevent their ending in canker. In orchards, the effects will be confined, in 

 a great measure, to those trees growing on the south-eastern side ; each tree 

 breaking, in a considerable degree, the rays of the sun from those behind, and 

 thus receiving the injury which the others would otherwise sustain. It is evident, 

 therefore, that if some tall fast-growing trees were planted at a sufficient distance 

 from the apple-trees, upon the south-eastern side, so as to break the force of the 

 sun's rays in the morning, this injury might in a great measure be prevented ; 

 but no such remedy can be applied to apple-trees growing in kitchen gardens, 

 standing detached from each other. Canker may also be produced by the 

 presence of iron, or some other pernicious ingredient, in the soil of particular 

 districts, which corrodes the roots in various places, and thus prevents the 

 necessary supply of sap. As this is most frequently caused by the sub-soil, care 

 should be taken to prevent the roots from penetrating into it, and when they have 

 got into it, the tree should be taken up, and have all the cankered roots cut off, 

 lightening the tops at the same time before replanting, by pruning out some of 

 the branches. 



These are the chief causes of canker, which have come under my own 

 observation; but there are probably many other circumstances, arising from 

 peculiarity of soil and situation, which may tend to produce the same injurious 

 effects. 



ON THE IRRITABILITY OF PLANTS. 



One of the most prominent features indicative of the existence of a vital prin- 

 ciple in plants, is the remarkable property they possess of being acted upon by 

 external stimuli, a property which seems to approach, in its character, to that 

 manifested by the animal creation. This curious and interesting subject has 



