CRUCIFER2E. ^MUSTARD FAMILY.) 33 



nec*ity none. Alpine summit of the White Mountains, New Hampshire. July. 

 Flowers 1-5, white. Pods 1' long, turgid, the convex valves 1-nerved: so 

 that the plant might as well be an Arabis ! (Eu.) 



* * Root perennial : leaves pinnate : flowers showy. 



4. C. prateitsis, L. (CUCKOO-FLOWER.) Stem ascending ; leaflets 7- 

 13, those of the lower leaves rounded and stalked; of the upper ones oblong or 

 linear, entire, or slightly angled-toothed ; petals (white or rose-color) thrice the 

 length of the calyx ; style short but distinct. Wet places and bogs, Vermont 

 to Ne\v Jersey, Wisconsin, and northward ; rare. May. (Eu.) 



* * * Root biennial or annual : leaves pinnate : flowers small. 



5. C. liii'SUta, L. (COMMON BITTER CRESS.) Mostly smooth in the 

 United States, sometimes hairy; leaves pinnate with 5-13 leaflets, or lyrate- 

 pinnatifid ; leaflets of the lower leaves rounded, angled or toothed ; of the upper 

 oblong or linear, often entire ; petals twice as long as the calyx (white) ; the 

 narrow pods and the pedicels upright : style shorter than the width of the pod. 

 (C. Pennsylvanica, Muhl.) Moist places, everywhere : a small delicate variety, 

 with narrow leaflets, growing on dry rocks, is C. VIRGINICA, Michx. (not of 

 Hb. Linn. ) May - July. (Eu. ) 



6. ARABIS, L. ROCK CRESS. 



Pod linear, flattened,- the valves plane or convex, 1-nerved in the middle, 01 

 longitudinally veiny. Seeds in a single row in each cell, usually margined or 

 winged. Cotyledons accumbent. Flowers white or rose-color. (Name from 

 the country, Arabia. See Linn. Phil. Bot., 235.) 



* Leaves all pinnately parted : root annual or biennial. (Aspect of Cardamine.) 



1. A. JLiulovicifma, Meyer. Nearly glabrous, diffusely branched 

 from the base (5' -10' high) ; divisions of the almost pinnate leaves numerous, 

 oblong or linear, few-toothed or incised ; flowers very small ; pods erect-spread- 

 ing, flat (9" -12" long, 1" wide), the valves longitudinally veiny (not elastic); 

 seeds wing-margined. (Cardamine Ludoviciana, Hook. Sisymbrium, Nutt.) 

 Open fields, &c., Illinois, Kentucky, and southward. April. 



# # Stem-leaves, if not the root-leaves, undivided : annuals or doubtful perennials. 



*- Seeds wingless or slightly margined. 



2. A. lyrata, L. Diffusely branched, low (4' -10' high), glabrous ex- 

 cept the lyrate-pinnatijid radical leaves ; stem-leaves spatulate or lanceolate, tapering 

 to the base, the upper entire; petals (white) twice the length of the calyx ; pods 

 spreading, long and slender, pointed with a short style. Rocks. April - June. 

 Radicle sometimes oblique. A variety ? from Upper Michigan and northward. 

 (Sisymbrium arabidoides, Hook.} has erect pods, and the cotyledons often ivhol- 

 ly incumbent. 



3. A. clniitata, Torr. & Gray. Roughish-pubescent, diffusely branched 

 (l-2 high), leaves oblong, very obtuse, unequally and sharply toothed ; those 

 of the stem half-clasping and eared at the base, of the root broader and tapering 

 into a short petiole ; petals (whitish) scarcely exceeding the calyx, pods spread* 

 intj, straight, short-stalked ; style scarcely any. New York and Illinois to Virgin- 



