FLORA OF THE DISTRICT OF COLUMBIA. 167 



1. Lepidium virginicum L. Peppergrass. 

 Fields and waste ground; abundant. May-July or later. Widely distributed in 



N. Amer. and naturalized elsewhere. 



The young plants are often used as "greens." 



Lepidium densifiorum Schrad. {L. apetaluin. of American authors) has been re- 

 ported from our region, but the specimens so determined are merely an apetalous 

 form of L. virginicum. 



2. Lepidium campestre L. 



Fields and waste ground; conlmon. May- June. Native of Eur.; j;^ddely natu- 

 ralized in N. Amer. 



3. Lepidium draba L. ' 



Collected a few times in waste ground about Washington. Apr.-May. Native of 

 Eur.; locally adventive in N. Amer. 



10. THLASPI L. Penny cress. 



1. Thlaspi arveuse L. 



Foimd only a few times about Washington and Alexandria; not collected recently. 

 Native of Eur. and Asia; often adventive in N. Amer. ^ 



Thlaspi perfoliatum L., with clasping stem leaves, was collected in waste groxind 

 near Virginia Avenue, Apr. 1899 {Steele). Native of Eur.; rarely adventive in N. 

 Amer. 



11. ALLIARLA. Adans. 



1. Alliaria officinalis Andrzej. Garlic mustard. 



Waste gi'ound or low woods along the Potomac; occasional. Apr.-May. {Sisym- 

 brium alliaria Scop.; Alliaria alliaria Britton.) 



Readily distinguished from all our other members of the family by the garlic-like 

 odor of the plant. 



12. CHEmiNlA Link. 



1. Cheirinia cheiranthoides (L.) Link. Wormseed mustard. 



Low ground along the upper Potomac; rare. June-July. Widely distributed in 

 N. Amer,; also in Eur. {Erysimum cheiranthoides L.) 



13. ERYSIMUM L. 



1. Erysimum officinale L. Hedge mustard. 



Waste ground; common. May-June. Native of Eur.; widely naturalized in N. 

 Amer. {Sisymbrium officinale Scop.) 



The typical form with hairy pods is rare in North America, but it occurs in our 

 region. The common form in North America {Sisymbrium officinale leiocarpum DC.) 

 has glabrous pods. 



14, NORTA Adans. 



1. Norta altissima (L.) Britton. Tumble mustard. 



Occasional in old fields and waste ground. May- June. Native of Eur.; widely 

 adventive in N. Amer., and in the West often a troublesome weed. {Sisymbrium 

 altissimum L.) 



Conringia oricntalis (L.) Dum., hare's-ear mustard, with clasping, entire, pale green 

 leaves, was collected in waste gi'ound, Washington, May, 1899 {Steele). Native of Eur. ; 

 occasionally adventive in N. Amer. 



16. HESPERIS L. 

 1. Hesperis mationalis L. Dame's bocket.s 



Occasional in woods and waste ground. May- June. Native of Eur.; sometime 

 Cultivated and escaping. 



