32 CRUCfFER^ 



secreting glands on the receptacle, one in front of each sepal. 

 There are two carpels, united to form a dry pod-like fruit. This 

 is generally compressed and dehisces by valves, when if elongated 

 it is termed a siliqua, if short and broad, a silicle. A partition, or 

 septum, dividing it into two chambers crosses its interior, either 

 parallel with the valves, i. e. across the longer transverse diameter 

 {/atisept), or at right angles with them {angustisept). 

 In some genera the pod is divided into several trans- 

 verse, I -seeded joints, when it is termed a lometitum. 

 The seeds are small, exalbuminous, arid oily. Their 

 relatively large cotyledons are variously placed with 

 reference to the radicle or primary embryonic root, 

 this root being either mciunbent, or folded against 

 the back of one cotyledon, or accumbent, folded 

 against the edges of both. The plants of this 

 Order are rich in nitrogen and sulphur, and have an 

 unpleasant odour when boiling or rotting. In a wild state they 

 are almost always pungent and even acrid ; but none of them are 

 poisonous, and many of them have valuable stimulant properties, 

 besides their use in medicine as antiscorbutics, or remedies against 

 scurvy. Under cultivation many of them become more succu- 

 lent and form some of our most useful vegetables, such as the 

 cabbage, turnip, radish, cress, and sea-kale. There are at least 

 1,200 species, mostly natives of the temperate zone, chiefly in the 

 Old World. They form a considerable proportion of the vegeta- 

 tion of Arctic latitudes. 



Sub-order I. SiliqudscE. Fruit a latisept siliqua 



Tribe i. Arabidece. Cotykdofis accumbent 



* Stigma 2-lobed 



I. Matthiola. — Stigma of two erect lobes ; flowers large, lilac 

 or violet. 



*2. Cheiranthus. — Stigma of two spreading lobes; flowers 

 large, yellow ; pod compressed with two prominent longitudinal 

 ribs. 



** Stigma small, undivided 



3. Radicula. — C(^/fx spreading; /^^cylindric; valves Q.on\Q\\ 

 seeds minute, 2-seriate. 



4. Barbarea. — Calyx erect; pod 4-angled ; seeds i -seriate. 



5. Arabis. — Pod linear, flat, obtuse ; valves with one longitu- 

 dinal rib or several veins, not elastic. 



