ROCKS AND WALLS, ETC. 



169 



careous rocks, limestone cliffs. The plant has the 

 rosette habit. The plant bears stiff hairs below. 

 The stems are erect or ascending. The radical 

 leaves are more or less narrowed into a stalk, 

 small, blunt, deep-green, fringed with forked and 

 simple hairs, lobed or toothed, the lobes oblong 

 or triangular. The stem-leaves are few, stalkless, 

 half-clasping. The flowers are white or cream- 

 colour, rather large. The petals are narrow, 

 wedge-shaped, nearly erect. The style is short. 

 The pods are few, distant, nearly erect, or spread- 

 ing, straight, three to six times as long as the 

 stalks. The valves are i -nerved. The seeds are 

 oblong, winged at the tip. The plant is 4-9 in. 

 high, flowering in April and May, and is a herb- 

 aceous perennial. 



Fringed Rock Cress (Arabis ciliata, Br.). The 

 habitat of this plant is walls, banks, rocky sea- 

 shores in Ireland. It is a local species. The plant 

 has the rosette habit. The plant is smooth or 

 fringed with hairs. The stem is erect. The 

 leaves are inversely ovate, smooth or hairy, or 

 fringed with hairs, toothed, nearly stalkless. The 

 stem-leaves are stalkless, rounded below, elliptic. 

 The flowers are white. The pods are few, broad, 

 erect, straight. The seeds are not winged, and 

 are close. The plant is 4-6 in. high, flowering in 

 July and August, and is a herbaceous biennial. 



Tower Mustard (Arabis glabra, Bernh. = Tur- 

 ritis glabra, L. = A. perfoliata, Lam.). The habi- 

 tat of this plant is dry banks, cliffs, dry rocky 

 places S. of Perth, and Ireland (Antrim). The 

 habit is erect. The stem is straight. The plant 

 is nearly smooth, or with few spreading hairs, 

 bluish-green. The radical leaves are stalked, in- 

 versely ovate, lobed, hairy, soon withering. The 

 stem-leaves are clasping, entire, auricled, smooth. 

 The flowers are pale -yellow, the petals erect. 

 The style is short. The pods are numerous, 

 crowded, slender, erect, on slender stalks. The 

 seeds are in 2 rows, very small, oblong, angled. 

 The plant is 1-3 ft. high, flowering in May to 

 July, and is a herbaceous biennial. 



Tower Cress (Arabis Turrita, L.). This plant 

 has been found on walls at Oxford, Cambridge, 

 and is naturalized on castle walls, Cleish, Kinross, 

 &c. 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, spread- 

 ing. The pods are flat, with a thick margin, 

 bent-back on the erect stalk, with no central vein, 

 but numerous, marked, netted veins running longi- 

 tudinally, 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 herb- 

 aceous perennial. 



Highland Whitlow Grass (Draba rupcstns, 

 Br.). The habitat of this plant is alpine, moun- 

 tain 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 in can a, 

 L.). The habitat of this species is alpine moun- 

 tain rocks and sea-coasts (sand-hills). The habit 

 is the rosette habit. The stems are erect, stel- 

 lately 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, flower- 

 ing in June and July, and is a herbaceous 

 perennial. 



Small Whitlow Grass (Draba muralis, L.). 

 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, 



