or GENERA. 283 



152, theoretical botanists ; those who study only species 

 and varieties, practical ones. 



In methodical arrangement, whether natural or artifi- 

 cial, every thing must give way to generic distinctions. 

 A natural system which should separate the species of a 

 good genus, would,by that very test alone, prove entirely 

 worthless ; and if such a defect be sometimes unavoid- 

 able in an artificial one, contrivances must be adopted to 

 remedy it ; of which Linnaeus has set us the example, 

 as will hereafter be explained. 



Generic characters are reckoned by Linnssus of three 

 kinds, the factitious, the essential, and the natural nil 

 founded on the fructification alone, and not on the inflo- 

 rescence, nor any other part. 



The first of these serves only to discriminate genera 

 that happen to come together in the same artificial or- 

 der or section ; the second to distinguish a particular 

 genus, by one striking mark, from all of the same natu- 

 ral order, and consequently from all other plants ; and 

 the third comprehends every possible mark common to 

 all the species of one genus. 



The factitious character can never stand alone, but 

 may sometimes, commodiously enough, be added to 

 more essential distinctions, as the insertion of the petals 

 in Agrimonia, Engl. Bot. t. 1335, Indicating the natur- 

 al order to which the plant belongs, which character, 

 though essential to that order, here becomes factitious. 



Linnaeus very much altered his notions of the essen- 

 tial character after he had published his Philosopliia Ho- 

 tanica, whence the above definitions are taken. Instead 

 of confining it to one mark or idea, he, in his Systema 



