FLORA Of THE DISTRICT OF COLUMBIA. 167 



1. Lepidium virginicum L. Pepperqrass. 

 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 densiflorum. Schrad. (L. apetalum of American authors) has been re- 

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

 form of L. virginicum. 



2. Lepidium campestre L. 



Fields and waste ground; common. May-June. Native of Eur.; widely 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 arvense L. 



Found 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 ground 

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



Amer. 



11. ALLIARIA Adans. 



1. AUiaria officinalis Andrzej. Garmo mustard. 



Waste ground or low woods along the Potomac; occasional. Apr -May. (Sisym- 

 brium alliaria Scop.; AUiaria alliaria Britton.) 



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

 odor of the plant. 



12. CHEIRINIA 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.) t 



13. ERYSIMUM L. 



1. Erysimum officinale L. Hedge mustard. 



Waste ground; common. May-Juno. 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 leioearpum 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 orienkdis (L.) Dum., hare's-ear mustard, with clasping, entire, pale green 

 leaves, was collected in waste ground, Washington, May, 1899 (Steele) . Native of Eur. ; 

 occasionally adventive in N. Amer. 



15. HESPERIS L. 



l. Hesperis matronalis L. Dame's rocket. i? 



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

 Cultivated and escaping. 



