THE NATURAL SYSTEM. 169 



CHAPTEE III. 



i THE NATURAL SYSTEM. 



886. The aim of thb Natural System is to associate plants into 

 groups and families according to their true natural likenesses and af- 

 finities, and thus to make an expression, so far as possible, of the Di- 

 vine plan in the System of Nature. 



887. It differs from the artificial arrangement : while that era- 

 ploys only a single character in classification, the natural system regards 

 the total organization, and seizes upon every character wherein plants 

 agree or disagree, and forms her associations only upon the principle of 

 natural affinity. Hence each member of any natural group resembles 

 the others, and a fair description of one will serve, to a greater or less 

 extent, for all the rest. 



888. The species and genera are formed on this principle of clas- 

 sification, as above stated, and are truly natural associations. Indi- 

 viduals altogether similar, cast as it were in the same mold, constitute 

 a species. Species agreeing in nearly all respects and differing but in 

 few constitute a genus. Thence the genera, associated by their re- 

 maining affinities into groups of few or many, by this same method are 

 organized into Natural Orders and other departments of the vegetable 

 kingdom. 



889. Relative value of characters. Although the natural 

 method employs every character, yet it does not regard all of equal 

 value or importance. As a rule, the higher the physiological import- 

 ance of any organ, the higher will be the value of the characters which 

 it afibrds. 



890. Because, (1) the less will It be subject to variation, and (2) the more gen- 

 eral in respect to other organs will be the resemblance of those plants which agree 

 in respect to that organ. Thus, first in value are those characters drawn from the 

 cellular tissue ; second, from the vessels, the stomata, the embryo, and albumen ; 

 third, from the axis and leaves, the stamens, pistils, and fruit ; fourth, from the pe- 

 rianth ; fifth, from the inflorescence and bracts. 



891. History of the natural method. Its foundation was first laid 1682, 

 by John Ray, of England. He separated the Flowering from the Flowerless plants, 

 and divided the former into Dicotyledons and Monocotyledons. Linnasus, about 50 

 years later, constrocted a fragment of the system, consisting of the names of 67 

 natural orders, without descriptions. But to Antoine do Jussieu is due the honor ol 

 the final establishment of this Metliod upon the true principles of natural affinity. 

 He arranged the genera then known (A. D. 1780) into 100 natural orders, defining 

 them with so much exactness, that nearly aJl have withstood the test of time ; and 

 have been adopted into our present systems. Eobert Brown contributed largely to 

 its completion and introduotiou into England, by the publication of his Flora of 



