144 DESCRIPTIVE BOTANY. PART I. 



being united together (<rv) in the 10th, and separate 

 (xof;) in the llth. The term Diclines indicates the 

 flowers of the l.'jth class to be unisexual ; and in the 

 two subdivisions of this class, the seeds are contained in 

 a pericarp or distinct vessel (a-yyc?) in the one, and art- 

 without it, or naked (yv/xvo?), in the other. The deri- 

 vation of the classes of the Alonocotyledones is evident. 



(136.) Artificial Arrangements. An artificial arrange- 

 ment proceeds upon the fact, that certain organs, in nearly 

 all the species included under the same genus, have a 

 great degree of constancy as to their number, relative 

 size, position, and other characters ; and these organs 

 are selected as the basis of the systematic arrangement. 

 Thus, for example, every species of the genus Ranun- 

 culus has more than twenty stamens, and these organs 

 are similarly circumstanced with respect to the other 

 floral whorls. The species of the genus Papaver, have 

 their stamens arranged like those of the last-mentioned 

 genus, and they are also numerous. These two genera 

 belong to different natural orders, but they and many 

 others are thrown together into the same artificial class, 

 characterised by the species having their stamens nume- 

 rous, and not attached to the calyx, the flowers also 

 containing both stamens and pistils. 



The natural groups, then, which we term genera, and 

 which are the lowest in the rank of subordination, are 

 not subdivided to suit the purposes of an artificial arrange- 

 ment ; but it is the higher groups only which are so. 

 There are certain cases, however, where it is advisable to 

 break through this rule, and to retain under the sarae 

 artificial class, several genera of a natural order, which do 

 not agree with the rule laid down for fixing their posi- 

 tion in the system. In other words, it would be too great 

 a violation of the natural group to which such genera 

 belong, to separate them from it. Thus, for example, 

 the greater number of those genera of the natural order 

 Leguminosse which have papilionaceous flowers, forming 

 the tribe Papilionaceie, have their filaments united round 

 the pistil, so thatnine are blended together, and one stands 



