Arabis. | VI. CRUCIFERZ. 29 
the valves flat or slightly convex, often marked with a distinct midrib or 
several longitudinal veins. Seeds more or less flattened, often winged. 
Radicle accumbent on the edge of the cotyledons or rarely obliquely 
incumbent. 
A numerous genus, spread over the temperate regions of the northern 
hemisphere, with a few extratropical species in the southern one. 
Stem-leaves undivided, rounded, or auricled at the base. 
Tall plants, with pods 3 inches or more long. 
Ripe pods erect or spreading. Plant glabrous. 
Auricles of the leaves pointed. Pods numerous, erect, 
crowded, the valves flat : 2 ‘ ss F ° 
Auricles of the leavesrounded. Pods loosely spreading, 
valves with a prominent midrib ; 3 , . Lrysimum orientale, 
Ripe pods turned downwards. Plant usually hairy . . 2. A, turrita, 
Plants seldom above a foot. Pod seldom 2 inches long. . 
Upper leaves clasping the stem 2 - ‘ . . 3. A, hirsuta. 
Upper leaves sessile, but not clasping the stem. 
Nearly simple perennial, with erect pods.- . ° . 4, A, ciliata. 
Slender branching annual, with spreading pods . . 5. A, thaliana, 
Stem-leaves narrowed at the base, the lower often pinnately lobed. 
Stem nearly simple. Radical leaves hispid, in a close tuft . 6. A. stricta. 
Stem branching at the base, in aloosetuft . : 5 . 7. A. petrea. 
1, A. perfoliata, 
Arabis albida or grandiflora, a south Russian species or variety of the 
A. alpina, is common in our gardens among the early-flowering perennials. 
The Lrysimum orientale, which might be mistaken for 4. perfoliata, is 
mentioned below under Hrysimum, of which it has the pods and seeds. 
1, A. perfoliata, Lam. (fig. 56). Glabrous Rockcress, Tower Mustard. 
—An erect annual or biennial, 2 feet or more high, perfectly glabrous 
except a few soft hairs at the very base, and usually glaucous. Radical 
leaves spreading but withering early, obovate-oblong, sinuate or pinnately 
lobed, with a few forked hairs.. Stem-leaves oblong-lanceolate, entire, 
clasping the stem by pointed auricles. Flowers small, white or pale straw- 
colour. Pods very long and narrow, erect and crowded in a long narrow 
raceme. TZurritis glabra, Linn, | 
On banks and roadsides and in open woods, generally distributed over 
-Europe and Russian Asia, except the extreme north, in northern America, 
and in Australia. Irregularly scattered over England and southern Scot- 
land, very rare in Ireland. FV. summer. The genus Turritis, which 
formerly comprised many svecies of Aradis, is still maintained by some 
botanists for this species and a few American ones, which have the two 
rows of seeds rather more distinct than in other species of Arabis. 
2, A. Turrita, Linn. (fig. 57). Tower Rockcress, Towercress.—A tall, 
stiff, erect biennial, approaching in size and appearance to the last species, 
but rough and somewhat hoary with very short forked or stellate hairs, 
Radical leaves spreading and stalked, stem-leaves oblong-lanceolate, sessile 
and clasping the stem by their rounded auricles, all slightly toothed. 
Flowers small, of a dirty yellowish white. Pods above 3 inches long, on 
short erect pedicels, but all curved downwards to one side, forming a long 
dense, nodding raceme. Seeds oblong, with a membranous border. 
In hedges, or shady banks, and under rocks, in the hilly districts of cen- 
tral and southern Europe, and establishes itself readily on old walls further 
north. Indicated at Oxford, at Cambridge, and in Kent, but evidently only 
introduced into Britain. £7. spring or early summer. 
