VI. CRUCIFER.E. 29 



A numerous genus, spread over the temperate regions of the northern 

 hemisphere, with a few extra-tropical species in the southern one. 



Stem-leaves undivided, rounded, or auricled at the base. 

 Tall plants, mth 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 1. A. perfoliata. 



Auricles of the leaves rounded. Pods loosely spreading, 



valves with a prominent midrib .... Erysimum orientate 

 Ripe pods turned downwards. Plant usually hairy . . 2. A. Turrita. 

 Plants seldom above afoot. Pod seldom 2 inches long. 

 Upper leaves clasping the stem entirely . . . . 3. A. hirsuta. 

 Upper leaves clasping the stem, coarsely toothed . . 4. A. alpina. 

 Upper leaves sessile, but not clasping the stem. 



Nearly simple perennial, with erect pods . . . . 5. A. ciliata. 

 Slender branching annual, with spreading pods . . 6. A. Thaliana. 

 Stem-leaves narrowed at the base, the lower often pinnately lobed. 

 Stem nearly simple. Radical leaves hispid, in a close tuft . 7. A. stricta. 

 Stem branching at the base, in a loose tuft . . . . 8. A. petrcea. 



Arabis albida or grandifiora, a South Russian species or variety of the 

 A. alpina, is common in our gardens among the early-flowering peren- 

 nials. Erysimnm orientate, which might be mistaken for A. perfoliata, is 

 described under that genus, of which it has the pods and seeds. 



1. A. perfoliata, Lam. (fig. 56). Glabrous, R., 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. Turritis 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 Scotland, very rare in Ireland. Fl. summer. The genus 

 Turritis, which formerly comprised many species of AroMs, 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 R., 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 

 central 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. Fl. spring or forty summer. 



3. A. hirsuta, Br. (fig. 58). Hairy R. A rather stiff erect annual or 

 biennial, attaining a foot or rather more in height, but often shorter, 



