FLOBA OF THE DISTRICT OF COLUMBIA. 169 



4. Arabis patens SulUv. 



Woods along the upper Potomac ; oceasional. Apr.-May. Minn, to Ala. 



5. Arabis dentata Torr. & Gray. 



Moist woods along the upper Potomac; occasional. Apr.-May. Northern states, 

 south to Va. 



19. CARDAMINE L. Bitter cress. 



Leaves simple, toothed or entire; stem bulblike at the base; petals about 10 mm. 

 long. 



Sepals green; petals white; plants glabrous 1. C. bulbosa. 



Sepals purplish; petals usually piu"plish; plants more or less hairy, with very diort 



hairs 2. C. douglassii. 



I^eaves pinnately divided; stems not bulblike at the base; petals less than 4 mm. 

 long. 

 Leaflets hairy on the upper surface, those of the basal leaves rounded; stamens 4. 



3. C. hirsuta. 

 Leaflets glabrous, comparatively narrow; stamens usually 6. 

 Leaflets of the stem leaves distinct, not running together along the rachis; plants 



of dry soil 4. C. parviflora. 



Leaflets of the stem leaves running together along the rachis, the rachis thus 

 winged; plants of wet soil 5. C. pennsylyanica. 



1. Cardamine bulbosa (Schreb.) B.S.P. 



Wet soil; frequent. Apr.-May. Eastern U. S. (C. rhomboidea DC.) 



2. Cardamine douglassii (Torr.) Britton. 



Wet soil along the upper Potomac; infrequent. Apr.-May. Northern states, south 

 to Md. 



Our specimens seem to be typical of the species except that the petals are mostly 

 white. The species is not very clearly distinct from G. bulbosa. 



3. Cardamine hirsuta L. 



Moist or wet soil in the region of Rock Creek Park and Chevj- Chase; frequent. 

 Apr.-May. Pa. to Nebr. and N. C, probably adventive; Eur. and Asia. 



4. Cardamine parviflora L. 



Dry woods; occasional. . Apr.-May. Eastern N. Amer. ; also in Eur. and Asia. (C. 

 hirsuta sylvatica of Ward's Flora.) 



5. Cardamine pennsylvanica Muhl. 



Wet soil, often along streams; common. Apr.-May. Eastern N. Amer. {C. hirsuta 

 of Ward's Flora, chiefly.) 



20. DENTARIA L. Pepper-root. 



Plants glabrous; leaflets of the basal leaves mostly ovate or rhombic-ovate, much 

 broader than those of the stem leaves; teeth of the leaflets short, usually rounded. 



1. D. heterophylla. 



Plants more or less h^-iry, at least above; leaflets of all the leaves similar, nan-owly 

 oblong to linear, the teeth long and naiTow, usually very acute... 2. D. laciniata. 



Dentaria diphylla L. has been reported from our region, but the species la not rep- 

 resented by specimens. It closely resembles D. heterophylla, but the rootstocks are 

 continuous, not jointed as in the latter species. 



1, Dentaria heterophylla Nutt. 



Moist woods; frequent, but the plants usually scattered. March-Apr. N. .T. to 

 Term. 



2. Dentaria laciniata Muhl. 



Moist woods; frequent. Apr.-May. Eastern N. Amer. 

 The flowers are shown in plate 30A. 



