490 ECOLOGY 



branch of knowledge, all schemes of classification confessedly are artifi- 

 cial, and yet an orderly arrangement of material is necessary. Even 

 where the various plant organs are well differentiated, they are not 

 treated rigidly in the following pages, but each subtopic is considered 

 where it seems the most appropriate; for example, food manufacture is 

 treated under leaves, conduction and mechanical support under stems, 

 and food accumulation under seeds, while vegetative reproduction is 

 considered chiefly under stems. 



