11 CRUCIFERJ5 83 



cabbage is one of those plants in which the stomata are 

 on the upper surface. They are protected by a waxy 

 secretion, so that water runs off in drops as off a duck's 

 back. The plant is found on maritime cliffs round 

 Europe as far as our southern counties. It is the 

 source of many forms of the cabbage, cauliflower, 

 brussels sprouts, etc. The seedling resembles that of 

 the Eadish (see p. 91). 



B. Sinapis (Charlock). — A cornfield weed with hispid 

 stem and leaves and bright yellow flowers. The bud 

 opens early in the morning, and the stigma is already 

 ripe. The anthers are still closed, so that in this stage 

 the flower must be cross -fertilised if fertilised at all. 

 The next morning the four longer stamens have 

 elongated and twisted round so as to face outwards, 

 away from the stigma. They form a sort of arch over 

 it. The third day the ovary has elongated, thus 

 bringing the stigma up to the anthers, and almost 

 ensuring self-fertilisation. 



B. nigra (Black Mustard). — As regards the structure 

 of the flower this species does not materially differ from 

 the preceding. The cotyledons also are similar, and as 

 in the Cabbage, Eadish, and other Crucifers they are 

 somewhat kidney-shaped (Fig. 51) and unequal. I will 

 endeavour to explain the reason for this when we come 

 to the Radish. 



B. campestris. — This is supposed to be the parent 

 stock of the Turnip {B. Napus). It is biennial, and 

 during the first year, when the stem remains very short, 

 the plant occupies itself by laying in a stock of nourish- 

 ment in the underground root formed from the portion 

 of the original stem (hypocotyl) between the cotyledons 

 and the upper part of the primary root. In the 

 following year the erect leafy and flowering stem is 

 produced at the expense of this store. 



DiPLOTAXIS 



The genus is distinguished from Brassica by having 

 the seeds arranged in two rows, whence the name. 



