46 
ON THE DISEASES OF PLANTS. 
The most effectual remedies for this affection are boiling water, as recommended 
by Mr. Beattie, in the Mem. Hort. Soc. of Edinburgh for 1827, and the " cream of 
lime/' applied with care to the stems ; or they may be scraped off, and the stems 
afterwards well washed with lime-water. 
Many insects attack the woody parts of plants, and trees in consequence become 
hollow : sometimes, again, the larvae of some insects curiously undermine the bark 
of various trees, living upon the liber and alburnum, and forming twisted paths 
running in all directions. What may be a cure for this last affection is unknown ; 
but if it be usual for the animals to enter in by wounds, the application of some 
plaster over these might be beneficial. 
Ulcerations of Stems or Canker. — Rough, brown, irregular surfaces, sometimes 
excavated, are often seen on the woody stems of plants. These are portions which 
have assumed the character of sloughing ulcers. These ulcerations generally go on 
increasing in size ; sometimes, however, by the efforts of the plant, a stop is put to 
the disease, and the part heals in the same way as wounds do. 
There is reason to believe that this disease usually commences in the liber, and 
its first appearance is indicated by a reddish-brown spot, circumscribed, generally 
slightly depressed, possessing more moisture than the surrounding parts : and in the 
centre, decomposition is usually indicated by a commencement of putrefaction. The 
disease spreads in all directions, involving all textures ; generally, it soon comes to ! 
the surface, and may at first be known by the falling in of the bark, from the loss 
of substance beneath by decomposition. The bark becomes opened out in its 
texture, and of a brown colour, and generally portions fall off in a decayed state as 
the disease proceeds, leaving sometimes large open surfaces, with rough edges of 
decayed bark, to become aggravated by external circumstances, and most particularly 
of insects. 
So various, and so opposite, are the opinions concerning the cause of this 
disease, that it is difficult, if not impossible, to discover the real one. Of eleven 
authors, the following table will show the various causes mentioned, and the 
number of supporters each opinion has : — 
Supporters. 
8. Wounds of the bark and wood. 
8. Bad soil and sub-soil, viz. wet — stiff clayey — cold clayey — cold wet — wet gravel — 
exhausted soils — mossy bottom. 
4. Injudicious pruning., 
3. Bruises. 
2. Gangrene of young shoots. 
2. Attacks of insects. 
2. Cold, wet seasons. 
2. Improper aspects. 
1 . Load of fruit. 
1. Frost injuring sap. 
1. Friction. 
Removal of the affected part by the knife, and covering the wound with plaster, 
as recommended by Forsyth, is the most usual method by which a cure is attempted 
