The Common Whitlow Grass.
Two species of Winter Cress (genus Barbarea) are common in waste land—the Common Winter Cress or Yellow Rocket (B. vulgaris), and the Early Winter Cress or American Cress (B. præcox). The former is an erect plant, from one to two feet high, with numerous, small, yellow flowers in a loose raceme, blooming from May to August. The radical leaves are pinnately divided, with a large, rounded, terminal lobe, and side lobes becoming smaller towards the base; and the upper leaves are oval and irregularly toothed. All the leaves are smooth and glossy, and of a deep green colour. The fruits are short, and thicker than the pedicels. A double variety of this flower is commonly cultivated in flower gardens.
The Yellow Rocket.
The Early Winter Cress is a very similar plant, flowering at the same time, but is of a more slender habit, and has narrower leaves, the upper of which are pinnately divided. The flowers are also larger, and arranged in a closer raceme; and the fruit is longer, but not thicker than the pedicel. This species is cultivated as a salad, and frequently occurs as a garden escape.
Two species of Sisymbrium are also very common—the Garlic Mustard (S. alliaria), also known as Sauce Alone and Jack-by-the-Hedge; and the Thale Cress or Wall Cress (S. Thaliana). The first named is one of the commonest of our hedgerow flowers. It grows to a height of one or two feet, and bears, from April to June, a corymbose cluster of pure white flowers, each about a quarter of an inch in diameter. The stem and leaves, when crushed, emit a distinct odour of garlic. The former is slightly branched; and the leaves are large, stalked, broadly cordate, with many prominent veins, coarsely toothed, and of a delicate green colour. The fruits are erect, about two inches long, on short pedicels.
The Thale Cress grows on dry banks and walls, and displays its minute white flowers from April to the end of the summer. The stem is erect, slender and branched, from six to ten inches in height; and the leaves, which are nearly all radical, are simple, oblong-lanceolate, toothed and downy. The fruits of this species are erect, narrow, with four obscure angles, and about twice as long as their stalks.
The Rape or Cole-seed (Brassica napus) is a cruciferous weed commonly occurring in cultivated ground, and often cultivated for its seeds. It grows from one to two feet high, and bears corymbose clusters of yellow flowers during May and June. Its root is fusiform (spindle-shaped), and all its leaves are smooth and of a sea-green colour. The lower leaves are lyrately pinnate, with toothed edges; and the stem leaves are ovate-lanceolate, acute, embracing the stem. The pods spread as they ripen.
The Wild Turnip (Brassica Rapa) is a very similar plant, producing its yellow flowers from April to July. Its root is tuberous and fleshy. The lower leaves are hairy and rough, and not of the glaucous green characterising the last species, while the upper leaves are glaucous and smooth.