4 PLANT STUDIES 
itself (reproduction). To the great work of nutrition many 
kinds of work contribute, and the same is true of repro- 
duction. Nutrition and reproduction, however, are the 
two primary kinds of work, and it is interesting to note 
that the first advance in the differentiation of a simple 
plant body is to separate the nutritive and reproductive 
regions. In the complex plants there are nutritive organs 
and reproductive organs ; by which is meant that there are 
distinct organs which specially contribute to the work of 
nutrition, and others which are specially concerned with 
the work of reproduction. The different kinds of work are 
conveniently spoken of as functions, each organ having one 
or more functions. 
7. Life-relations. In its nutritive and reproductive work 
the plant is very dependent upon its surroundings. It 
must receive material from the outside and get rid of waste 
material ; and it must leave its offspring in as favorable 
conditions for living as possible. As a consequence, every 
organ holds a definite relation to something outside of it- 
self, known as its life-relation. For example, green leaves 
are definitely related to light, many roots are related to 
soil, certain plants are related to abundant water, some 
plants are related to other plants or animals (living as 
parasites), etc. A plant with several organs, therefore, 
may hold a great variety of life-relations, and it is quite a 
complex problem for such a plant to adjust all of its parts 
properly to their necessary relations. The study of the 
life-relations of plants is a division of Botany known as 
Ecology, and presents to us many of the most important 
problems of plant life. 
It must not be supposed that any plant or organ holds 
a perfectly simple life-relation, for it is affected by a great 
variety of things. A root, for instance, is affected by light, 
gravity, moisture, soil material, contact, etc. Every or- 
gan, therefore, must adjust itself to a very complex set of 
life-relations, and a plant with several organs has so many 
