250 EXPLANATION OF THE 



the two preceding, and Pursh, adopting this plan, ha$ 

 arranged them all in one class, termed Diclinia in allu- 

 sion to their separate flowers. 



" Such are the principles of the Linnaean Classes and 

 Orders, which have the advantage of all other systems 

 in facility, if not in conformity to the arrangement of 

 nature ; the latter merit they do not claim. They are 

 happily founded on two organs, not only essential to a 

 plant, but both necessarily present at the same time ; 

 for though the Orders of the 14th and 15th Classes 

 are distinguished by the fruit, they can be clearly as- 

 certained even in the earliest state of the germen. 



Like all human inventions, however, this system bas 

 its imperfections and difficulties. If we meet in gardens 

 with double or monstrous flowers, whose essential or- 

 gans of fructification are deformed, multiplied, or 

 changed to petals ; or if we find a solitary barren, or 

 fertile blossom only ; we must be at a loss, and in such 

 cases could only guess at a new plant from its natural 

 resemblance to some known one. But the principal 

 imperfection of the System in question consists, not 

 merely in what arises from variations in number or 

 structure among the parts of a flower, against which 

 system could provide, but in the differences which 

 sometimes occur between the number of Stamens, 

 Styles, kc. in different plants of the same natural ge- 

 nus. Thus, some species of Ccrastium have only 4, 

 others, 5 Stamens, though the greater part have 10. 

 Lychnis dioica has the Stamens on one plant, the Pistils 

 on another, though the rest of the genus ha3 them unit- 

 ed in the same flower ; and there are several similar 

 instances ; for number in the parts of fructification is 

 no more invariable than other characters, and even 

 more uncertain than such as are founded on insertion, 



