TO BOTANY. 103 



CHAP. XXIX. 

 OF GENERIC DISTINCTIONS. 



HAVING now gone through the explanation of the 

 Classes and Orders of the system, we come to the 

 distinctions of the Genera. These, by the theory 

 of the Sexual System, are to be regulated by the 

 fructification only. The parts of fructification known 

 to the earlier botanists were few, and might be well 

 thought insufficient for distinguishing the vegetable 

 productions of nature : they therefore had recourse 

 to the habit of plants and other circumstances ; and 

 by this means a great number of genera were esta- 

 blished, which the new system is obliged to reject. 

 Of these we shall give the reader an ample list of 

 instances in Chap. 31st. 



The fructification being admitted as the only foun- 

 dation of the generic distinctions, all vegetables that 

 agree in their parts of fructification are to be put 

 together under one genus ; and all such as differ in 

 those parts are to be divided. The characteristic 

 mark of each genus is to be fixed from the number, 

 figure, proportion and situation of all the parts : but 

 as there are few genera wherein all the parts are con- 

 stant in every one of the species, we ought, wherever 

 it is possible, to fix upon some one single circum- 

 stance that is constant, and make it the essential cha- 

 racter. This in most genera may be had : thus the 

 essence of Brunella, Torenia, Euphrasia, Alyssum, 

 and Crambe, lies in. the denticles of the stamina " 3 

 that of Curcuma, Chelone, Bignonia, and Martynia 

 in a mutilate stamen ; the Ranunculus is distinguished 

 by its nectarium, which is a pore in the claws of its 

 petals ; Hydrophyllum by the same part, which in 

 that genus is a closed chink in the laciniae of the co- 

 3 c 4 



