CRUCIFERJE. (MUSTARD FAMILY.) 65 



3. Petals white, much longer than the calyx : pods ovoid or globular : leaves undivided, 

 or the lower ones pinnatifid : root perennial. (Armoracia.) 



7. N. lactlStre, Gray, Gen. 111. 1, p. 132. (LAKE CRESS.) Aquatic; 

 immersed leaves 1 - 3-pinnately dissected into numerous capillary divisions; 

 emersed leaves oblong, entire, serrate, or pinnatifid ; pedicels widely spreading ; 

 pods ovoid, one-celled, a little longer than the style. (N. natans, var. Americanum, 

 Gray. Armoracia Americana, Arn.) Lakes and rivers, N. E. New York to 

 Illinois and southwestward. July - Aug. Near N. amphibium. 



8. N. ARMORACIA, Fries. (HORSERADISH.) Root-leaves very large, ob- 

 long, crenate, rarely pinnatifid ; those of the stem lanceolate ; fruiting pedicels 

 ascending; pods globular (seldom formed); style very short. ( Cochlearia Armo- 

 racia, L.) Roots large and long ; a well-known condiment. Escaped from 

 cultivation into moist ground. (Adv. from Eu.) 



2. LEAVENWORTHIA, Torr. LEAVENWORTHIA. 



Pod broadly linear or oblong, flat ; the valves nerveless, but minutely reticu- 

 late-veined. Seeds in a single row in each cell, flat, surrounded by a wing. 

 Embryo straight ! or the short radicle only slightly bent in the direction which 

 if continued would make the orbicular cotyledons accumbent. Little biennial 

 or hyemal annuals, glabrous and stemless, with lyrate root-leaves and short 

 one - few-flowered scapes. (Named in honor of the late M. G. Leavenworth.) 



1. L. Michauxii, Torr. On flat rocks and barrens, S. E. Kentucky and 

 southwestward: rare. March -May. Scapes 2' -4' high. Petals purple, 

 rose color, or nearly white, with a golden yellow or yellowish base, or rarely 

 yellow throughout 1 (L. aurea, Torr.), cuneate-obcordate or emarginate; the 

 flowers rather large for the size of the plant. 



3. DENTAHIA, L. TOOTHWORT. PEPPER-ROOT. 



Pod lanceolate, flat, as in Cardamine, but broader. Seedstalks broad and 

 flat. Cotyledons petioled, their margins somewhat infolding each other. 

 Perennials, with long, horizontal, fleshy, sometimes interrupted, scaly or toothed 

 rootstocks, of a pleasant pungent taste ; the simple stems leafless below, bear- 

 ing 2 or 3 petioled compound leaves about the middle, and terminated by a 

 single corymb or short raceme of large white or purple flowers. (Name from 

 dens, a tooth.) 



1. D. diph^lla, L. Rootstock long and continuous, toothed ; stem-leaves 2, 

 similar to the radical ones, close together, of 3 rhombic-ovate coarsely toothed 

 leaflets ; petals white. Rich woods, Maine to Kentucky. May. Rootstocks 

 5' - 10' long, crisp, tasting like Water-Cress. 



2. D. maxima, Nutt. Rootstock interrupted, forming a string of thick toothed 

 tubers; stem-leaves (2-7) mostly 3 and alternate; leaflets 3, ovate, obtuse, coarsely 

 toothed and incised, often 2-3-cleft; petals pink. (D. laciniata, var. <*, Torr. 

 fr Gr.) Northern New York (Watertown, Crawe; Utica, Paine) to Penn. : 

 rare. May. Seldom taller, but the leaves often smaller, than in No. 1. 



3. D. heteroph^lla, Nutt. Rootstock a chain of 2 or 3 narrow-oblong and 

 obscurely toothed tubers; stem-leaves 2 or 3, alternate (rarely opposite), divided into 



5 



