ORDEK SILIQUOS.E. 
A flower of thp 
cruciform tribe is 
i a represented at A, 
i Fig. 139;— at 5 are 
seen the six sta- 
1 mens arranged In 
/ two sets, the four 
c 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 6, the claw ; at 
B 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 
have dicotyledonous 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 vegetables for the 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 the orders of the class Didynamia. 
Order Siliculosa. 
The first 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, (Lepidium,) and the shepherd's 
purse, (Thlaspi,) afford examples of this order. At Fig. 138, d, is a 
representation of the silicula or pod of the Thlaspi. The plants 
found here, belong to the natural family SiliquoscB, the properties of 
which are nutritious and medicinal. 
Order Siliguosce. 
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. 138, a, is 
the w ah-fiower, {Cheiranthus ;) the calyx consists of four oblong se- 
pals ; the petals are obovate, spreading with claws as long as the 
calyx. At b, appear the six stamens divested of the petals ; the 
germ is cylindrical, as long as the stamens ; c, shows the sihque 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 in 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. 
""Desftribe Fvj^. 139— How many orders in tlie class Tetradynamia']— Order Silicu 
.osa — Oruur SUjuuosiu— Recapiiulation 
