Arabis 



Cruciferae 



505 



0~ ~33 

 Map 1038 



Arabis virginica (L.) Poir. 



Jan. 



Feb. 



Mar. 



Apr 



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Miles 



o 56 



Map 1040 



Arabis pycnocarpa 

 var. adpressipilis Hopkins 



stellate-pubescent; plants simple, erect, usually 6-12 dm high 



1. A. glabra. 



Pods flattened, 1.5-2 mm wide; seeds winged; basal leaves more or less 

 pubescent. 

 Mature pods erect; stem and stem leaves glabrous; seed in 2 distinct rows. 



8. A. Drummondii. 



Mature pods spreading or loosely ascending; usually the base of the stem 

 and a few of the lowest leaves more or less pubescent; seed, when 

 young, in 2 distinct rows, many aborting and leaving the mature, 

 perfect ones in 1 row almost as wide as the cell. (See excluded species 



no. 273, p. 1053.) A. divaricarpa. 



Stem leaves (at least the upper) without auricled bases. 



Plants much branched, usually less than 3.5 dm high; basal leaves lyrate-pin- 

 natifid; stem leaves rarely over 4 cm long, linear-oblong, obtuse, entire or 

 with a few teeth; pedicels of fruit ascending; mature pods ascending, mostly 



20-50 mm long; seed in 1 row, wingless 9. A. lyrata. 



Plants simple or nearly so, mostly 5-15 dm high; basal leaves dentate or lyrate- 

 lobed; stem leaves tapered at both ends, generally much more than 4 cm 

 long, more or less deeply toothed; pedicels of fruit recurved; mature pods 



pendent, mostly 50-80 mm long; seed in 1 row, broadly winged 



10. A. canadensis. 



1. Arabis virginica (L.) Poir. (Arabis virginica (L.) Trel. of Gray, 

 Man., ed. 7 and Britton and Brown, Illus. Flora, ed. 2.) Virginia Rock- 

 cress. Map 1038. Locally frequent to common in fallow cornfields in the 

 southern part of the state. It is usually in moist soil associated with Poa 

 Chapmaniana and Myosotis virginica, indicating a slightly acid habitat 

 which, I think, controls its distribution. 



Va. to 111., south w. to Fla. and Tex.; westw. to Calif, and Lower Calif. 



2. Arabis pycnocarpa Hopkins. (Rhodora 39: 112. 1937.) (Arabis 

 hirsuta of American authors.) Hairy ROCKCRESS. Map 1039. Infrequent 

 to rare in the state and probably absent from some of the central counties. 

 It grows in sandy soil in alluvial bottoms, in crevices of rocks, and on 

 rocky slopes and high banks of streams. Since all of my specimens are 

 from the borders of streams and lakes, its affinity for them is apparent. 



