82 THE CBITCIFES FAMTLT. 



In muddy and watery places, throughout Europe and Russian Asia, from 

 the Mediterranean to the Arctic regions, and in North America. Pretty 

 frequent in England and Ireland, but decreasing considerably in Scotland. 

 Fl. summer and winter. 



4. Great 'Watercress. Nasturtium amphibium, Br. 



{Sisymbrium, Eng. Bot. t. 1840. Armoracia, Brit. Fl. Yellow Cress.) 

 A taller and more erect plant than either of the two preceding, attaining 

 2 or 3 feet. Leavps less divided, sometimes narrow lanceolate, 3 to 4 inches 

 long, and only slightly toothed, more frequently deeply toothed or pinnately 

 lobed, sometimes divided to the midrib into narrow segments. Flowers 

 yeUow, larger than in the two last, the petals longer than the calyx. Pod 

 straight, ellipticil, about 2 lines long, or sometimes shorter and almost 

 globular, the style much longer than in the other species. 



In moist meadows and watery places, throughout Europe and Russian 

 Asia, Generally distributed over England, Ireland, and southern Scotland, 

 but not very common. Fl. summer. The shortness of the pod in this and 

 some varieties of the marsh W. has induced some botanists to remove them 

 to SiliculoscB, and associate them with the Horseradish in the genus Armo- 

 racia or Roripa, a junction which appears purely artificial. 



Y. ROCKCRESS. ARABIS. 



Annuals or perennials, usually erect and hairy, at least at their base, with 

 a spreading tuft of radical leaves, wliich are occasionally lobed, the stem- 

 leaves undivided, sessile or stem-clasping ; the flowers white, or, in a few 

 exotic species, purple. Pods long and linear, the stigma nearly sessile, 

 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 obhquely 

 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. 

 Tiill plants^ wftk pods 3 inches or mure long. 

 Bipe pods erect or spreading. Plant glabrous. 

 Auricles of the leaves pointed. Pods numerous, erect, 



crowded, the valves flat 1. Glabrous M. 



Auricles of the leaves rounded. Pods loosely spreading, 



valves with a prominent midrib Eastern Erysimum, 



Ripe pods turned downwards. Plant usually hairy ... 2. Tower M. 

 Fhint seldom above a foot. Fod seldom 2 inches Ixjng. 



Upper leaves clasping the stem 3. Sairy S. 



Upper leaves sessile, but not clasping the stem. 



Nearly simple perennial, with erect pods 4. Fringed Jt. 



Slender branching annual, with spreading pods .... 5. Thal^ S. 

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



Stems nearly simple. Radical leaves hispid, in a close tiift . 6. Bristol It. 

 Stems branching at the base, in a loose tuft 7. Northern It. 



Arabis albida or grandijlora, a south Russian species or variety of the 

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

 The eastern Erysimum, which might be mistaken for the glabrous RocJc- 

 cress, is mentioned below under Erysimum, of which it has the pod and 

 seeds, 



