CltVCIFEUM. 



47 



4. Great Watercress. Nasturtium amphibium, Br. (Fig. 54.) 



(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. Leaves less divided, some- 

 times 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 yellow, 

 larger than in the two last, the petals 

 longer than the calyx. Pod straight, 

 elliptical, about 2 lines long, or some- 

 times 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, Fig. 54. 



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 Siliculosce, and associate 

 them with the Horseradish in the genus Armoracia or Morijpa, a junc- 

 tion 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, which 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 flat- 

 tened, 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 1. Glabrous R. 



