4 PLANT EELATIONS. 



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 ate 

 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 



