Ml 
This tree is frequently covered with a fungus, 
which, if it should be shown to be capable of 
degenerating into the wheat fungus, would offer 
an easy explanation of the effect. 
There is some reason to believe, from the re- 
searches of Sir Joseph Banks, that the smut in 
wheat likewise is produced by a very small fungus 
which fixes on the grain: the products that it 
affords by analysis are similar to those afforded by 
the puff-ball ; and it is difficult to conceive, that 
without the agency of some organized structure, 
so complete a change should be effected in the 
constitution of the grain. 
The misletoe and the ivy, the moss and the 
lichen, in fixing upon trees, uniformly injure their 
vegetative processes, though in very different de- 
grees. They are supported from the lateral sap ves- 
sels, and deprive the branches above of a part of 
their nourishment. 
The insect tribes are scarcely less injurious than 
the parasitical plants. 
To enumerate all the animal destroyers and 
tyrants of the vegetable kingdom, would be to give 
a catalogue of the greater number of the classes in 
zoology. Every species of plant almost is the pe- 
culiar resting-place, or dominion of some insect 
tribe; and from the locust, the caterpillar, and 
snail, to the minute aphis, a wonderful variety of 
the inferior insects are nourished, and live by their 
ravages upon the vegetable world. 
I have already referred to the insect which feeds 
on the seed leaf of the turnip. 
it 
