NATURAL CLASSIFICATION. 



113 



which is founded upon one of these two great functions of 

 the vegetable kingdom, must necessarily be as natural as that 

 which has a reference to the other function. 



This principle, indeed, is opposed by the commonly recei- 

 ved idea, that the parts of fructification are properly the 

 most essential and important. It is opposed by the general 

 practice of the founders of systems, who regard only the parts 

 of propagation, and derive from them the principles of ar- 

 rangement ; but this happens principally because we usually 

 find fewer differences in the organs of nourishment, and be- 

 cause, in order to discover these differences, dissection is pre- 

 viously required. Hence, in order to proceed securely to 

 work, and not to throw unnecessary difficulties into the study, 

 we must view the Organs of Fructification as the chief basis 

 of Classification. 



170. 



As in an organised body all the parts have a mutual in- 

 fluence, and are connected with one another, important differ- 

 ences in the organs of one function must of necessity draw 

 along with them differences in the structure of the parts 

 which belong to another function ; and it is a very important 

 principle, that the entire structure of plants is different when 

 important alterations are found in the seed. Plants, whose 

 seeds contain an unevolved embryon and rich albumen, have a 

 completely different internal structure of stem, leaves, flowers, 

 and commonly even a different numerical proportion, from 

 plants, whose seeds contain a completely developed embryon, 

 and have little or no albuminous substance. 



In many instances this has even an influence on the nature 

 of the secreted juices, because these derive their character 

 only from the nature of the separate organs. Thus the co- 

 loured juices in the Hypericeae and Guttiferae, the milky juice 

 of the Euphorbiae, and the aromatic ingredients of the La- 

 biatae, are well known examples of this influence of natural 

 affinity even on the constitution of juices. The theory of 

 medicines may, in this view, derive advantages from the na- 

 tural arrangement of plants. 



II 



