CHAPTER XIX 
PLANT INDUSTRIES 
292. Origin of plant cultivation. In the various chapters of 
this book we have constantly recognized the relation of plants 
to the common interests of men. It is important, however, 
that special uses of plants in the industries should receive 
separate attention. 
In the early stages of civilization plants were used by men 
for food, clothing, and fuel, for the construction of houses 
and boats, and in many other ways. In order to obtain those 
plants that would best serve any of these uses, some obser- 
vation and experiment with plants doubtless had to be made. 
Indeed, primitive people are often well versed in the nature 
of wild plants, so that they know what to select and where 
to find the desired plants in the seasons when they are avail- 
able. Wild plants that were good for food or possibly for 
medicines were cared for early in the history of civilization. 
We can only guess at the ways in which they were first 
watched and protected, hut they were cared for by people who 
foresaw a need for the products of these plants when mature. 
With such activities as these agriculture came into existence. 
At this time comparatively little was known of the nature of 
plant life, and therefore early agriculture was relatively simple. 
As more has been learned about plant life, plant products have 
improved in quality or in quantity, or in both. As populations 
become more dense, greater demands are made upon plants 
as a means of supplying adequate food and clothing. 
293. Problems of plant industries. Each of the plant indus- 
tries involves two kinds of problems. First, there is the prob- 
lem of carefully applying what science has already discovered 
308 
