XXVI. 
THESTUDY OF THE INJURIES AND DISEASES OF PLANTS. 
By Alfred T. Brett, H.D. 
Read at Watford, 12 th April, 1889 . 
I wish to direct attention to a study which has not hitherto been 
undertaken hy our Society—that of the injuries and diseases of 
plants. I hope to be able to show that it is a legitimate subject 
of research,—interesting in its nature, always before us both in 
town and country, and likely to have many practical and useful 
results. 
I should like for a moment to explain how my attention has 
been directed to it. One day our Society was going over Kew 
Gardens under the direction of the Eev. George Henslow, and I 
gave expression to the regret that in our county, and perhaps in 
Great Britain, we have found all the plants that we are likely to 
discover, this field of discovery being thus closed. He replied that 
it is quite true that systematic botany is nearly complete, at least 
in this country, and probably we shall not make many more dis¬ 
coveries; yet, he said, physiological botany (the life-history of 
plants) is a study quite in its infancy, and there is a great deal 
of work to do, and a great deal for botanists to learn. 
In following up this idea, it occurred to me that if the healthy 
life of plants is only just beginning to he studied, the unhealthy or 
diseased life of plants might afford an interesting, useful, and 
practical subject for study. The very word ‘disease’ frightens 
some people, but it need not, especially when it is confined to the 
vegetable kingdom. Nature proceeds in her operations on certain 
definite lines, and usually produces uniform results. When nothing 
interferes with her laws, the result is normal or healthy life; hut 
when she is interfered with, the result is abnormal or diseased life. 
Of course one is as much under law as the other. While some of 
us are studying the healthy life of plants, others may be studying 
the diseased life of plants. The study of one may throw light on 
the study of the other. Not only may vegetable pathology throw 
light on vegetable physiology, hut even enlighten animal physio¬ 
logy and pathology. And as we derive much pleasure and profit 
from the vegetable kingdom, to study its diseases may he useful in 
order to prevent them. 
Sir James Paget is one of the best pathologists in Europe. 
Lately in a lecture he said that when a young man he derived 
great benefit from the study of botany; among other things it 
made him accurate in observation and careful in classifying. In a 
lecture on the nature of cancer he did not think it beneath him to 
refer to some of the diseases of plants in order to elucidate and 
explain the nature of cancer. I therefore wrote to him and asked 
him to tell me the best hooks to read on the diseases of plants, and 
