HOMOLOGIES 



327 



just as the morphological study of plants forms the scientific 

 basis of systematic botam^ To a certain extent the concep- 

 tions involved are necessarily abstract, or, so to say, dia- 

 grammatic; for the parts of plants are thus viewed only in 

 one aspect, and for the sake of being able to think of them 



Fig. 281. — Diagram of a typical fioweriiig piaut showing the principal 

 parts and their homologies. Root-members are black; stem-members, 

 shaded with lines running lengthwise; leaf-members, shaded with lines 

 across; and sac-members, unshaded. (Original.) 



simply many facts are deliberately left out of account. The 

 conclusions reached nevertheless may be true so far as they go, 

 and are valuable aids to fuller knowledge; but the student 

 should remember that natural objects are never diagram- 

 matic and that Nature does not draw the sharp lines of dis- 

 tinction which we may find it useful to assume. 



