FLORA 07 THE DISTRICT OP COLUMBIA. 45
S. SOBGHASTBTJM
I. NYMPHAEA
9. LEPIDIUM L
Stem leaves with tapering bases. Plants glabrous or nearly so; pods shallowly notched at the top 1, L. viiginicum.
Stem leaves with auricled clasping bases.
Pods deeply notched, winged; branches of the inflorescence densely and finely hairy 2. L. campestre.
Pods pointed, not winged; branches of the inflorescence glabrous or nearly so.
3, L. diaba.
FLORA OF THE DISTRICT OF COLUMBIA. 167
1. Lepidium virginicum L. Peffekgbabs . 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 demijlorum Schrad, (L. apdalum of American authors) has been re- ported from our region, but the specimens so determined are merely an apetaloue 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. THLASFI 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 perfolvxtum L., with clasping stem leaves, was collected in wast© ground near Virginia Avenue, Apr. 1899 (Steele). Native of Eur.; rarely adventive in N.
Amer.
11. ALLIABIA Adans.
1. Ainmitt offioinalis Andrzej. Garlic muhtart>.
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. CHEIBINIA Link.
1. Cheixinla cheiranthoides (L.) Link. Wormseed mustard.
Low ground along the upper Potomac; rare. June-July. Widely distributed in N, Amer.; also in Eur. (Ert/simum cheiranthmde# L.^
13. ERYSmUM 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 Iriocarpum 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 allissimum L.)
Conringia orkntalis (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.
16. HESPERIS h.
l. Hesperis matronalis L. Dame's booket.b
Occasional in woods and waste ground. May-June. Native of Eur.; sometime Cultivated and escaping.
16, ABABEDOPSIS (DO.) Schur.
1. Arabidopsls thallana (L.) Britton. Mouse-ear cress.
Fields; common. March-May. Native of Eur, and Asia; widely naturalized in N. Amer, (Sixymbrium thalianum Gay; Stenophragma thaliana Celak.)
17, CAMPE Dulac. Winter cress.
Lobes of the leaves mostly 4-8 pairs; pods stout, sharply angled, on very stout short pedicels 1, C, vema.
Lobes of the leaves mostly 1-4 pairs; pods slender or stout, obtusely angled, on slender pedicels.
Pods erect; petals pale yellow 2. C. stricta.
Pods spreading or ascending; petals bright yellow 3. C. barbarea.
1. Campe vema (Michx.) Heller.
Woods, fields, and waste ground; abundant. Native of Eur.; extensively natural- ized in eastern N. Amer. (Barbarea praecox R. Br.; B. vema Aschers.)
This and the other species are much used as "greens," and are commonly seen in the markets in spring.
2. Campe stricta (Andrzej.) W. F. Wight.
Fields; abundant. Apr .-May. Native of Eur. Asia, and northern N. Amer.; with us doubtless adventive. (Barbarea vulgaris of Ward's Flora; B. stricta Andrzej.)
8. Campe barbarea (L.) W. F. Wight.
Fields; apparently not common. Apr .-May. Native of Eur. and northern N.
Amer.; naturalized in eastern N. Amer. (Barbarea vulgaris R . Br.; B, barbarea MacM.)
18. ARABIiS L. Rock cress.
Lower leaves pinnately divided; stem leaves mostly linear and entire, tapering at the base. Pods ascending 1, A. lyrata.
Lower leaves merely toothed; stem leaves all or mostly broader than linear, often toothed.
Stem leaves, at least the upper ones, long-tapering at the base, not auricled, more or less toothed; pods drooping. Plants hairy 2, A. canadensls.
Stem leaves never tapering at the base, more or less clasping and auricled; pods ascending or spreading.
Plants glabrous throughout; upper leaves mostly entire, long-tapering at the apex. Pods recurved-spreading 3. A. laevigata.
Plants hairy, at least below; upper leaves all or nearly all conspicuously toothed, never long-tapering at the apex.
Petals more than twice as long as the calyx; pods strongly ascending; seeds narrowly winged 4. A, patens.
Petals equaling or very slightly exceeding the sepals; pods spreading; seeds not winged 6. A. dentata.
Arabia hirsuta (L.) Scop, was reported from Sandy Landing by Ward, but the species is not represented by specimens from our region.
1. Arabia lyrata L,
On rocks along the upper Potomac; frequent; also collected once along the Eastern Branch, probably adventive there. March-June. Widely distributed in N. Amer ; also in eastern Asia.
%. Arabls canadensis L. Sickle-pod.
Woods along the Potomac and Rock Creek; frequent. May-June. Eastern IT. S.
3. Arabls laevigata (Muhl.) Foir.
Woods, often on rocks; frequent along the upper Potomac, occasional elsewhere.
Apr.-May. Eastern N. Amer.
FLORA OF THE DISTRICT OP COLUMBIA. 169
4, Arabia patens Sulliv.
Woods along the upper Potomac; occasional. Apr.-May. Minn, to Ala.
5. Arabia dentate Torr. & Gray.
Moist woods along the upper Potomac; occasional. Apr-May. Northern states, south to Va.
19. CABDAMINE L. Bitter chess.
Leaves simple, toothed or entire; stem bulblike at the base; petals about 10 mm.
long.
Sepals green; petals white; plants glabrous 1. C. bulbosa.
Sepals purplish; petals usually purplish; plants more or less hairy, with very short hairs. 8. C. douglassii.
Leaves pinnately divided; stems not bulblike at the base; petals less than 4 mm.
long.
Leaflets hairy on the upper surface, those of the basal leaves rounded; stamens 4.
3. C. hirsute.
Leaflets glabrous, comparatively narrow; stamens usually 6.
Leaflets of the stem leaves distinct, not running together along the rachis; plants of dry soil 4. C. parrifloca.
Leaflets of the stem leaves running together along the rachis, the rachis thus winged; plants of wet soil @ C. pennsylvanica.
1. Cardamine bulbosa (Schreb.) B.S.P.
Wet soil; frequent. Apr.-May. Eastern U. S. {C. rhomboidea DO.) 9. Cardamine douglassii (Torr.) Britton.
Wet soil along the upper Potomac; infrequent. Apr-May. Northern states, south to Md.
Our specimens seem to be typical of the species except tha* the petals are mostly white. The species is not very clearly distinct from C. bulbosa.
3. Cardamine hirsnta L.
Moist or wet soil in the region of Rock Creek Park and Chevy Chase; frequent.
Apr.-May. Pa. to Nebr. and N. C.f probably adventive; Eur. and Asia.
4. Cardamine parviflora L.
Dry woods; occasional. Apr.-May. Eastern N, Amer.; also in Eur. and Asia. (C, hirsute sylvatica of Ward's Flora.)
5. Cardamine pennsylvanica Muhl.
Wet soil, often along streams; common. Apr.-May. Eastern N. Amer. (C, hirsuta of Ward's Flora, chiefly.)
20. DENTAMA L. Pepper-root.
Plants glabrous; leaflets of the basal leaves mostly ovate or rhombic-ovate, much broader than those of the stem leaves; teeth of the leaflets short, usually rounded.
1, D. heterophylla.
Plants more or less hairy, at least above; leaflets of all the leaves similar, narrowly oblong to linear, the teeth long and narrow, usually very acute...2. D. laciniata.
Dentaria diphylla L. has been reported from our region, but the species is not rep - resented by specimens. It closely resembles D. heterophylla, but the rootstocks arc continuous, not jointed as in the latter species.
1. Dentaria heterophylla Nutt.
Moist woods; frequent, but the plants usually scattered. March-Apr, N. J. to Tenn.
2. Dentaria laciniata Muhl.
Moist woods; frequent. Apr.-May. Eastern N. Amer.
The flowers are shown in plate 30A.