Tower Cress (Arabis Turrita, L.)

This plant has been found on walls at Oxford, Cambridge, and is naturalized on castle walls, Cleish, Kinross, etc. It was first noticed in the vicinity of botanic gardens, from which it was originally doubtless an escape. The habit is erect. The plant is stellately downy. The stems are robust, leafy. The radical leaves are stalked, entire, on the barren branches of the rootstock. They are entire, stellately hairy, toothed, elliptic, narrowed into a stalk, the stem-leaves heart-shaped, clasping, long, narrow. The flowers are pale-yellow, and bear bracts. The petals are inversely ovate, lance-shaped, spreading. The pods are flat, with a thick margin, bent-back on the erect stalk, with no central vein, but numerous, marked, netted veins running longitudinally, large, long, on one side of the stalk, with thick valves. The seeds are oblong, with a membranous wing. The plant is 1-2 ft. high, flowering in May and June, and is a herbaceous perennial.

Yellow Whitlow Grass (Draba aizoides, L.). The habitat of this plant is rocks and walls. The plant has the rosette or cushion habit, being densely tufted. The leaves are all radical, the aerial stems being smooth scapes. The leaves are linear, rigid, fringed with hairs, shining, keeled, the margins and tip white, cartilaginous. The scape is rigid. The flowers are golden or bright yellow at first, then white, in short racemes, elongated in fruit. The petals are scarcely notched. The stamens are as long as the petals. The style is as long as the pouch is broad. The pods are oblong, smooth, acute. There are 10-12 seeds in each cell. The plant is 2-5 in. high, flowering from March to May, and is a herbaceous perennial.

Highland Whitlow Grass (Draba Rupcstns, Br.)

The habitat of this plant is alpine, mountain rocks. The plant has the rosette habit. The rootstock is slender. The stem or scape bears few leaves, and is very short, branched, each stem bearing a dense tuft of leaves and 1-3 short scapes. The radical leaves are stellately downy, oblong, lance-shaped, flat, nearly entire, tufted, toothed, fringed with hairs. The scapes are 1-3, slender, wavy, the leaves stalkless, stellately downy. The flowers are white, few, small. The petals are slightly notched. The stamens are not so long as the petals. The style is short. The pods are small, straight, oval, oblong, blunt, hairy, on straight stalks, which are erect to spreading. The plant is 1-2 in. high, flowering in June and July, and is a herbaceous perennial.

Twisted Pod Whitlow Grass (Draba Incana, L.)

The habitat of this species is alpine mountain rocks and sea-coasts (sand-hills). The habit is the rosette habit. The stems are erect, stellately hairy, simple or branched. The rootstock is often woody and long. The radical leaves are lance-shaped, oblong, toothed, spreading, forming a dense rosette, stellately downy. The stem-leaves are few, clasping, more or less erect. The flowers are numerous, white, in a long raceme, on short stalks. The petals are twice as long as the calyx. The style is short. The pods are linear, oblong, lance-shaped, twisted, longer than the stalks, which are erect to spreading, smooth or nearly so, blunt or acute, variable. The seeds are numerous. The plant is 2-20 in. high, flowering in June and July, and is a herbaceous perennial.