This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
The habitat of this plant is limestone rocks and walls, hills. The habit is the rosette habit. The rootstock is slender. The stems are slender, wavy, leafy, branched, more or less erect or prostrate, stellately hairy. The radical leaves are narrowed below, small, inversely ovate. The stem-leaves are broadly ovate, heart-shaped, blunt, coarsely toothed, few, distant, clasping, hairy. The flowers are white, on spreading horizontal stalks, in short racemes, longer in fruit. The petals are not notched, and are very small. The pods are smooth, flat, blunt, linear to oblong, horizontal, the stalks longer. There is no style. The seeds are very small, 10-12. The plant is 4-12 in. high, flowering- in April and May, and is a herbaceous annual or biennial.
Whitlow Grass (Erophila prcecox, Stev. = E. brachycarpa (Ord.), D.C.). - The habitat of this species is walls and dry places. From E. vema it differs in the flattened pods, which are inversely ovate to oblong-, rounded, one to one-and-a-half times as long as broad. The cells contain 12-20 seeds. The flowers are white. The plant is 1-4 in. high, flowering from March to June, and is a herbaceous perennial.
Erophila inflata, Wats., Hook, fil. - The habitat of this plant is mountain rocks, and the plant is rare. The pods are turgid, round in section, ovoid to oblong, twice as long as broad, and the cells contain 20-40 seeds. The flowers are white. The plant is 1-3 in. high, flowering from March to July, and is a herbaceous annual.
E. virescens, Jord. - In this plant the hairs are all or nearly all simple. The stem is slender, sub-erect, flexuose, short. The leaves are more or less narrow lance-shaped, oblong or ovate. The sepals are clear-green, the silicles 4x2 cm., the style longer, the plant 6-7 cm.
The habitat of this plant is dry soils, hedgebanks, cultivated ground, walls, etc. It is a native of wood borders, stream banks, rocks, and woods. The plant has the rosette habit. The stems are slender, leafless or nearly so, much-branched. The leaves are mainly radical, entire, toothed, downy, oblong, lance-shaped, stalked, the stem-leaves narrow, stalkless, entire or toothed. The flowers are small, white, on slender, spreading stalks. The pods are spreading or ascending, slender, curved, bluntly 4-angled, linear, twice as long as the stalks, not convex dorsally, the lateral longitudinal veins obscure. The seeds are very small, oblong, not furrowed. The plant is 6 in. to 1 ft. high, flowering from May to September, and is a herbaceous annual.
The habitat of this plant is waste places, limestone rocks, and walls. The plant has the rosette habit. The stem is simple, leafless, hairy. The leaves are hairless, long-stalked, wavy or divided nearly to the base, egg-shaped, lance-shaped, blunt. The scapes are slender, ascending. The flowers are yellow, on stalks of the same length, the petals 2-3 times as long as the sepals, inversely egg-shaped, notched or abrupt, roundish, with a short claw. The style is not narrowed below, stout, straight. The pods are slender, narrowed at the top only, the valves flat, nerveless. The seeds are in two rows (hence Diplotaxis). The plant is 6-18 in. high, flowering between June and September, and is a herbaceous annual or biennial.