174 



ORDER SILIQUOS.E. 



A flower of the 

 cruciform tribe is 

 represented at A, 

 Fig. 139 ;— at B are 

 seen the six sta- 

 mens arranged in 

 two sets, the fom' 

 at a being longer 

 than the two " at 

 b ; at c are two 

 glands between the 

 short stamens and 

 the germ ; — At C is 

 a petal consisting 

 of a, the border, 

 and b, the claw ; at 

 D is the pod, which 

 is a silique ; a rep- 

 resents the valves ; 

 b the seeds, as al- 

 ternately fastened to the edges of the partition, (dissepiment,) which 

 divides this kind of pericarp into two cells. The cruciform plants 

 liave dicolyledonous seeds, polypetalous corollas, and the stamens 

 are hypogynous. They are herbs, with leaves alternate. The flow- 

 ers are usually yellow or white, seldom purple. 



Plants of the class Tetradynamia are never poisonous ; they fur- 

 nish many important veg'etables forth® table; their properties are 

 antiscorbutic. The orders in this class are two, depending on the 

 comparative length of the pods; this distinction is less definite than 

 that which marks tile orders of the class Didynamia. 



Order Siliculosa. 



The Jirst Order contains plants which produce a short and round 

 pod called a silicula ; a distinction in this order is made between such 

 plants as have pods with a notch at the top, and such as have none, 

 or are entire. The Pepper-grass, (Lepidntm,) and the shepherd's 

 purse, (IVilaspi,) aflford examples of this order. At Fig. 133, d, is a 

 representation of the silieula or pod of the Thlaspi. The plants 

 found here, belong to the natural family Siliquosce, the properties of 

 which are nutritious and medicinal. 



Order Siliquosce. 



The second Order contains cruciform plants with long and narrow 

 pods; as the radish and mustard. The cabbage (Brassica) is an 

 exotic ; the turnip is a species of the same genus. At Fig. I3S, a, is 

 the wall-flower, {Cheiranlhus ;) the calyx consists of four oblong se- 

 pals ; the petals are obovate, spreading with claws as long as the 

 cslyx. At 6, appear the six stamens divested of the petals ; the 

 germ is cylindrical, as long as the stamens ; c, shows the silique or 

 pod ; the valves are concave, and a thin membranous partition: 

 divides the silique into two parts. 



In this lecture we have pointed out the most important characters 

 of the two classes which depend upon considerations derived from 

 the number and comparative length of the stamens. Both classes 

 we found to have two orders^ not as in the preceding classes, de- 

 pending upon the styles ; but m the one class, on the situation of the 

 seed as lying in the calyx, or enclosed in a seed vessel; in the other 

 class, from the comparative length of the pericarp or pod. 



DtSLTibe Fii,'. 130— How many ordtis in the class Tetradynamia?— Order Siiicu- 

 .osa — Oruer SihquoscB— Recapitulation 



