CHAPTER EIGHTEEN 
DISEASES OF PLANTS 
As a Blight is the most common and dangerous Distemper 
that Plants are subject to, so I shall endeavour to explain 
by what Means Vegetables are affected by it; and if I shall 
be so happy, from the Observations I have made, to dis- 
cover the Cause of it, the Remedy may then be more easily 
found out, and the Gardener will with more certainty hope 
for Success from his Care and Labour. 
From an Old English Garden Book (1726) 
ALL the vegetables of the garden are plants that 
have roots, stems, and leaves. Each of these parts has 
different work to do; and in the plants there are vessels 
to carry water, minerals, and foods between the different 
parts. 
The garden plants all have chlorophyll, a green color- 
ing matter which makes them able to use the energy of 
the sunlight in building food. They are, therefore, self- 
supporting ; they can make their own food from carbon 
dioxid taken from the air, and from water and minerals 
taken from the soil. As we have learned in earlier 
chapters, this is one of the main reasons why they are so 
valuable to man as food plants. 
The garden plants also produce seeds, which usually 
pass through a resting period before the young plants 
resume growth. In this way the plants that live but 
one year are able to pass the winter months. 
In all these respects garden plants are like the many 
kinds of trees, shrubs, and herbs that are abundant and 
conspicuous all about us. Because of these qualities, 
and especially because of their power to produce seeds, 
these plants are considered to be the higher forms of 
plant life. 
286 
