PLANT INDUSTRIES 319 
that a tree or a bush filled with a large amount of perfect 
fruit or berries is not a usual occurrence in nature. Horti- 
culture attempts to use the plant as a machine for producing 
a large amount of perfect fruit; to secure this result we must 
make careful use of every known agency that will help the 
machine to work well and that will protect it from those 
things that in nature would injure it or reduce the value of 
its product. The state agricultural experiment stations pub- 
lish instructions for spraying orchard and garden plants. 
299. Gardening. Gardening has to do in the main with the 
production of plants whose growing parts men use for food. 
The list of plants thus used is a long and constantly increas- 
ing one, and although the gardening industry is extending 
rapidly, it is not keeping pace with the increasing demands 
for its products. Both vegetable and flower gardening have 
problems distinct from those of other plant industries. Both 
are highly intensive in their nature and present new problems 
in such matters as soil selection and replenishment, cultivation, 
harvesting, marketing, and the prevention of disease. 
Wild plants of many kinds are used as medicines, and some 
of these are grown in large quantities in gardens especially 
designed for that purpose.? 
300. Plants and the soil. The plants that constitute the 
basis of plant industries depend in large measure upon their 
relation to the soils in which they live. Soils are very differ- 
ent from one another, some by their nature prohibiting the 
life of certain kinds of plants and making possible the growth 
of others. Some of the facts about differences in soils are 
known, others are matters of vigorous argument between 
scientists, and still other problems are recognized by all as 
still wholly unsolved. That the structure of the soil has 
much to do with its appropriateness for plant life is generally 
recognized. Our coarsest gravelly soils consist of much rock 
1** Wild Medicinal Plants of the United States.’? Bulletin 89, Bureau of 
Plant Industry, U.S. Dept. Agr., 1906; ‘' American Medicinal Leaves and 
Herbs,’’ Bulletin 219, Bureau of Plant Industry, U.S. Dept. Agr., 1911. 
