CLASS TETRADYNAMIA. 135 



CHAPTER XXII. 



OP THE CLASS TETRADYNAMIA.* 



In the plants of this class, known to you already as 

 the Crucifer2£, and equally natural in the present 

 artificial system, there are 6 stamens, arranged com- 

 monly in 2 sets, and of an unequal length ; 2 being 

 shorter than the other 4, in consequence of a small 

 gland interposed betwixt their base and that of the 

 germ. Unlike the plants of the simple sixth class, the 

 flowers of this are easily distinguished by producing a 

 calyx and corola of only 4 parts, or in symmetry with 

 the 4 longer, and more perfect stamens. The fruit 

 also, as in JJidynamia, alone, forms the distinction of 

 the orders ; but here the orders both belong to the 

 same natural group, and are so closely related as to 

 pass insensibly almost into each other. They are 

 founded merely on the comparative length of the pod 

 or silique ; the first being termed Siliculosa, and the 

 second order Siliqjjosa. 



Four stamens, instead of 6, the ordinary number, 

 appears to be the symmetrical proportion of this class ; 

 and constant examples of a number below 6 are not 

 wanting in nature ; as for example, in Lepidium vir- 

 ginicum there are only 2 to 4 ; and in Draba caroli- 

 niana, where there are also 2 of the 6 commonly want- 

 ing. The 2 other short stamens then with their glands, 

 which seem to form a separate system in the cruci- 

 ferous flowers, have been assumed, perhaps rather 

 boldly, as so many interposed rudiments of other flow- 

 ers ; and it is indeed asserted, that instances have oc- 

 curred of their so developing themselves. That a sin- 

 gle stamen with its gland may be occasionally the 

 type of a flower, is not so extraordinary a circum- 



* From ri<7 taps, four, and Mm/jih, power, the power of four. 



