126 ILLINOIS ACADEMY OF SCIENCE 
ences between perennials and annuals; (b) a study of herbs as 
classified according to their value to man, as: valueless or 
“wild,” those of economic value or “cultivated, and those 
undesirable or injurious, which we call ‘‘weeds.’”’ Uncultivated 
herbs are of interest chiefly synecologically as the associates of 
trees in their different groupings and as indicators of the char- 
acteristics of the environment, as hydrophytic, xerophytic, 
etc. As the subject of taxonomy has to do chiefly with the 
wild herbs, it is frequently included under ecology today. 
Cultivated herbs and their attendant, though undesirable 
forms, are considered more from the autecological side. Their 
reactions to and tolerance of extremes of temperature and 
moisture and chemical conditions, are of course of chief im- 
portance. Original habitat and distribution and to some ex- 
tent taxonomic relations, are also important as indicating suit- 
ability for certain environments. This value is testified to by 
the systematic search for new varieties carried on by the 
United States Department of Agriculture. Herbs vary greatly 
in their reactions to environmental factors, and should be 
grouped as far as possible along the lines of similar behavior, 
Knowledge of these groups should be as complete as possible, 
but a thorough study of the ecological reactions of a few type 
genera and species should be included in any comprehensive 
course in ecology. 
3. The ecology of lower types of plants is not treated 
separately, but on account of economic importance under the 
special subject of bacteriology, mycology, etc. 
II, RELATION OF ECOLOGY TO AGRICULTURE. 
A. Purpose and Scope of Agriculture. The subject of agri- 
culture is extremely complex and even the terminology is not 
uniform in usage. Even the word agriculture itself is em- 
ployed in a general and a special manner. It is used here in 
the general sense of the cultivation of plant products from the 
soil. Its complexity is made evident by consideration of the 
varied ends sought, which include size, strength, water content, 
and chemical contents of stem, leaves, roots, flowers, fruit, and 
special parts such as fibers, cork, etc. 
The resulting subdivisions of the subject following largely 
the usage of Bailey’s Cyclopedia of Horticulture, are: Agri- 
