ii.J OF PLANTS. in 



characters of their flowers ; more so, at least, than are 

 the species of larger genera. 



3. Recollect, then, that in the scientific name of a plant 

 we always state both the name of the genus and that of 

 the species to which it belongs. The generic name pre- 

 cedes. Thus Ranunculus bulbosits, Ranunculus acris, and 

 Ranunculus repens are three distinct species of Buttercup 

 familiar to botanists, always admitted as distinct, although 

 their differences are so slight that the untrained eye 

 might regard them as belonging to the same species. 

 Observe, however, the closely reflexed sepals of R. bul- 

 bosusj the spreading sepals, round peduncle, and stem, 

 without runners of R. acris ; and the spreading sepals, 

 furrowed peduncles, and stem with runners of R. repens. 

 The brief characters which suffice to distinguish these 

 species from each other are said to be diagnostic. It will 

 be observed that the diagnoses of species rest upon com- 

 paratively slight modifications of structure. The diagnoses 

 of genera rest upon characters of higher importance (cha- 

 racters more constant in the group than those used to dis- 

 tinguish species), and so on for the groups superior to the 

 genus, the characters of each of which embrace, as we 

 have already shown, those of all their subordinates. The 

 method of denoting every plant and animal by two names, 

 a generic and specific, on a uniform plan, was invented by 

 Linnaeus, and has become universally adopted. 



The method of grouping genera into higher groups, 

 according to their resemblance in characters of succes- 

 sive degrees of constancy, though indicated by the same 

 eminent man, has been the "work of many collaborators, 

 amongst whom the names of Jussieu, Brown, and De 

 Candolle are pre-eminent. 



4. Precisely as we group species under Genera, so we 

 group genera under Natural Orders. The Natural Orders 

 again (to which substantive names are applied for con- 

 venience), under Divisions ; the Divisions under Sub- 

 classes and Classes, as we have already pointed out. 

 Thus, the characters of a Class are common not only to 

 the Subclasses and Divisions, but to the Natural Orders, 

 Genera, and Species included in that Class. It follows, 

 therefore, that the characters of a Class must be more 

 constant and more general than those of a Subclass or 



