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 dry banks, rocks, walls, dry places generally. The habit is the rosette habit. The stems are hairy (hence hirsuta), with hairs closely pressed, the hairs simple, spreading, leafy, slender, numerous. The radical leaves are more or less narrowed below, shortly-stalked, toothed, the stem-leaves stalkless, or half-clasping, blunt, with spreading auricles, or heart-shaped below. The flowers are small, white, the petals spreading. The pods are erect, narrow, slender, straight, closely pressed. The style is short. The seeds are distant, with a narrow wing. The plant is 9-18 in. high, flowering from June to August, and is a herbaceous biennial.
The habitat of this plant is mountains. The plant was formerly regarded as a sub-species of C. officinalis. It has more or less the rosette habit. It is a more slender plant, with smaller leaves. The radical leaves are broadly heart-shaped, blunt, entire or rather obscurely lobed, the upper stem-leaves triangular, clasping', 3-lobed, or broadly egg-shaped, with 4-6 teeth. The pods are rhomboid to oblong, narrowed both ends, inversely egg-shaped. The style is short. The plant is 4-12 in. high, flowering from June to August, and is a perennial or biennial.
Cochlearia micacea, E.S.M. - The habitat of this species is high Scottish mountains. The plant is regarded as a variety of the last. It differs in being a small, prostrate plant. The leaves are small. The pod is narrower, 1 1/2 -3 times as long as broad. The plant is 2-4 in. high, flowering from June to August, and is a herbaceous biennial.
The habitat of this species is sandy and gravelly places. The plant has the rosette habit. The stems are numerous, or solitary, slender, ascending, with one or two small leaves. The leaves are radical, numerous, flat, divided nearly to the base, the lobes larger upwards, or rounded, spoon-shaped, entire. The flowers are white, in a corymb, then a raceme, the 2 outer petals twice as long as the rest, unequal. The stamens bear scales. The style is very short. The pods are notched, winged, on short, slender, spreading stalks. The plant is 5-12 in. high, flowering in June and July, and is a herbaceous annual.