504 Cruciferae Descurainia 



2997. DESCURAINIA Webb. & Barth. 



[Detling. Revision of the North American species of Descurainia. Amer. 

 Midland Nat. 22: 481-520. 1939.] 



1. Descurainia brachycarpa (Richardson) 0. E. Schulz.* (Sisym- 

 brium canescens var. brachycarpon (Richardson) Wats, and Sophia pin- 

 nata (Walt.) Howell.) Map 1037. Plants referred to this species are ex- 

 ceedingly variable and some authors divide the forms into varieties and 

 species. I find no character that divides our Indiana specimens satisfac- 

 torily and I think it best to consider our forms as a species complex until 

 further study of the group. I reported Descurainia intermedia for the state 

 but I now refer the specimen to this complex. 



This species prefers very sandy soil and is generally found in railroad 

 ballast. I have found it also on gravelly slopes and in very sandy soil in a 

 creek bottom. It has doubtless been introduced into Indiana from the west. 



Que. to Wash., southw. to Tenn., Mo., Tex., and Calif. 



3001. ARABIS L. 



Plants with basal and stem leaves pinnatifid, much branched at the base, the branches 

 widely spreading; plants rarely 4 dm high; pedicels rarely more than 5 mm long; 



pods about 2 cm long; seed narrow-winged, in 1 row 1. A. virginica. 



Plants not as above. 



Stem leaves more or less auricled at the base and often clasping. 



Stems and leaves more or less pubescent throughout (at least below the middle); 



seeds in 1 row. 



Mature pods erect or strongly ascending, 30-50 mm long; plants erect, often 



divided at the base; leaves pubescent mostly on the margins and midrib 



beneath (sometimes some of the upper ones entirely glabrous) ; seed oblong, 



about 1 mm long, narrowly winged. 



Pubescence of stem spreading or subspreading, predominantly of simple hairs. 



2. A. pycnocarpa. 



Pubescence of stem strictly appressed, often giving a strigose appearance, 



predominantly of forked hairs 2a. A. pycnocarpa var. adpressipilis. 



Mature pods spreading; plants erect or decumbent; leaves pubescent all over, at 

 least on the lower surface (except in A. viridis var. Deamii). 

 Plants erect, not branched at the base (at least not conspicuously so), growing 

 on dry rocky or gravelly slopes; pedicels mostly 10-18 mm long. 



Pubescence of simple hairs; basal leaves usually somewhat pinnatifid 



3. A. viridis var. Deamii. 



Pubescence mostly forked; basal leaves merely dentate 4. A. patens. 



Plants lax, conspicuously branched at the base, the branches decumbent or 

 ascending, growing in moist, alluvial soil along streams and in moist soil 



at the base of slopes; pedicels mostly 1-3 mm long 5. A. dentata. 



Stem leaves glabrous, or only the base of the stem and basal leaves and a few of 



the lowest stem leaves pubescent. 



Plants with the middle cauline leaves long and narrow, generally 5-15 mm wide 



and 7-13 cm long, spreading or rarely erect, entire or coarsely dentate; 



pedicels mostly 5-10 mm long; pods recurved, spreading, 6-11 cm long; seed 



in 1 row, winged, about 1.5 mm long including the wing 6. A. laevigata. 



Plants not as above. 



Pods terete or 4-sided, about 1 mm wide; seed in 1 row or in some pods the 

 seed interruptedly in 1 and 2 rows, wingless; stem glabrous or somewhat 

 hirsute at the base; stem leaves glabrous; basal leaves more or less 



* The name of this plant now becomes Descurainia pinnata subsp. brachycarpa 

 (Richardson) Detling. (Amer. Midland Nat. 22: 509. 1939.) 



