PRINCIPLES OF CLASSIFICATION. 31 



pear indicated by Nature herself. Some are very 

 evident, as Grasses, Umbelliferous Plants, Com- 

 pound Flowers, the Orchis tribe, Palms, Ferns, 

 and Mosses. Others are more obscure, and many 

 plants cannot yet be referred to any such Orders or 

 Classes. 



78. Artificial ones (76) are contrived for human con- 

 venience, to assist the memory, and to promote the 

 determination and discrimination of plants. Such 

 constitute the Linntean system, founded on the 

 Stamens and Pistils (58, 59); those of Tournefort 

 and llivinus upon the Corolla (54) ; and those of 

 Ray, and several other authors, upon the Fruit (6 1) 

 and Seed (62). 



79. Linnaeus first pointed out the distinction betwixt 

 a Natural and an Artificial System ; but Bernard 

 de, Jussieu and his nephew Antoine Laurent de Jus- 

 sieu, first formed and published a Natural System, 

 reduced to a regular form upon scientific principles. 



80. Linnaeus contended that human science was not 

 -; yet competent to give definitions, or technical cha- 

 racters, of Natural Classifications. 



81. Adanson indeed undertook this, and A. L. de 

 Jussieu has founded his System, published at Paris 

 in 1789, upon such characters; which though in- 

 complete, and liable to various exceptions, is of 

 great use as a key to a Natural Arrangement (79). 

 In proportion however as it serves this purpose, and 

 is dependent on definitions, it becomes in many 



