FLORA 07 THE DISTRICT OP COLUMBIA. 45
S. SOBGHASTBTJM
I. CYPEBUS L
6. PLEUBOPTERT7S
Flowers with none of the sepals keeled or winged.
Stems ascending or reclining, armed with very numerous recurved prickles;
ocrese persistent 7. TB-ACA€X ON.
Stems erect, unarmed; ocreae fragile, soon withering 8. FAGOPYBUM.
1. RTTMEX L. Dock.
Plants small, with slender creeping propagating roots; foliage strongly acid; leaves hastately lobed X. B. acetosella.
Plants large; rootstocks stout, deep-seated; foliage slightly or not at all acid; leaves not lobed.
Leaves flat, bright or pale green.
Pedicels several times as long as the wings; each of the 3 wings usuafly bearing a well-developed tubercle at maturity 2. B. verticillatus.
Pedicels about equaling the wings; usually only one of the wings tuberculare.
3. B. altissimus.
Leaves wavy or crisped at the margins, dark green.
Wings with a few spreading bristle-like teeth 4. B. obtusifolius.
Wings entire or nearly so.
Blades of lower leaves narrowed at base; usually only one of the wings tuber- culate 5. B. patientia.
Blades of lower leaves cordate or obtuse at base; all 3 of the wings usually tuberculate... 6. B. crispus.
1. Bumex acetosella L. Sheep sorrel.
Dry fields and rocky hillsides; abundant. Summer. Nearly throughout X. Amer.;
naturalized from Eur.
*
2. Bumex verticillatus L. Swamp dock.
Swamps and moist alluvial situations; several localities, principally along the upper Potomac. May-July. Eastern N. Amer.
3. Bumex altissimus Wood.
Moist alluvial situations; not uncommon, especially along the Potomac. Apr - June. Eastern U, S.
4. Bumex obtusifolius L. Bitter dock Waste places; common, Sumraor. Nearly throughout N. Amer.; naturalized front Eur.
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FLORA OF THE DISTRICT OF COLUMBIA.. 145
5. Burner patientla L.
Dumps and waste places; apparently not very common. May-Tune. North- eastern states westward; naturalized from Eur.
6. Bumex crispus L. Narrow dock.
Roadsides and waste places; common. Summer. Naturalized from Eur., nearly throughout N. Amer.
Hybrids between this species and R. obtusijolius are reported by Ward.
2, POLYGONUM L. Knotweed.
Stem and branches angled.
Leaves plicate; fruits erect, on stout pedicels fi. P. tenne.
Leaves flat, the margins merely re volute; fruits drooping on slender reflexed pedicels.
6. P. douglasli.
Stem and branches terete or nearly so, usually striate.
Plants chiefly prostrate, the branches mostly basal; flowers comparatively small, the sepals less than 2 mm. long.
Leaves usually acute; achene ovoid, acute 1. P. aviculare.
Loaves obtuse or subacute; achene broadly ovoid, constricted below the apex, often conspicuously so, 2. P; buxifoime.
Plants erect or ascending, more or less diffusely branched above the base; flowers larger, the sepals 2-3 mm. long.
Leaves elliptic to obovate, obtuse to acutish, yellowish green 3. P. erectum.
Leaves linear-elliptic to lance-elliptic, acuminate, green (not yellowish).
4. P. atlanticum.
1. Polygonum aviculare L. Knotgrass.
Cultivated and waste places; a common weed. Summer and autumn. N. Amer.
and Eur.
2. Polygonum buxiforme Small.
Waste ground; apparently rare locally, a single record. July. Widely distributed in N. Amer.
8. Polygonum erectum L.
Moist or dry situations; common. July-Sept. Widely distributed in N. Amer.
4. Polygonum atlanticum (Robinson) Bicknell.
Vicinity of Government fish ponds, a single record (July, 1902). Adventive; native of salt marshes along the N. Eng. coast.
5. Polygonum tenue Michx.
Dryish, more or less sandy slopes; not very common. July-Sept. Eastern N. Amer.
6. Polygonum douglasli Greene.
Old circus grounds; a single record (Aug. 7, 1912). Western U. S.; adventive east- ward.
3. TOVABA Adans.
J. Tovara virglnica (L.) Raf. Jumfseed.
Low moist woods and alluvial thickets; common. Late summer. Eastern N. Amer.
4. PEE SIC ARIA Mill.
Spikes solitary or in pairs.
Plants usually aquatic; leaves floating, long-petioled, obtuse or acutish; spikes ovoid or oblong, not more than 2.5 cm. long, the peduncles glabrous... 1. P. amphibia.
Plank usually of swamps or stream banks, erect or ascending; leaves short-petioled, acuminate; spikes 3-10 cm. long, the peduncles hispid..2. P. muhlenbergii.
60289—19 10
Spikes several or numerous,
Ocrese not fringed with bristles.
Flowers white, greenish, or pink, borne in Blender, elongate, usually drooping spikes 2-8 cm, long 3. P. lapathifolia.
Flowers deep pink or rose-colored, borne in thick oblong-cylindric erect spikes 2-5 cm. long 4. P. pennsylvanica.
Ocrese fringed with bristles.
Sepals conspicuously gland-dotted.
Spikes drooping; stamens 4 or G; achene granular and dull 6. P. hydropiper.
Spikes erect; stamens 8; achene smooth and shining 6, P. punctata.
Sepals not gland-dotted.
Plants up to 2.5 meters high, coarse; ocrem often with a spreading herbaceous border; leaves long-petioled, the blades broad, ovate or oblong; spikes drooping 7. P. orientalis.
Plants 20-100 cm. high; ocreae without a spreading border; leaves sessile or nearly so, the blades narrow, linear-lanceolate to oblong-lanceolate; p-pikes erect.
Plants annual; spikes short-cylindric, dense. Leaves usually with a dark triangular or crescent-shaped spot near the middle 8. P. mitis.
Plants perennial; spikes slender, often interrupted 9. P. hydropiperoides
1. Persicaria amphibia (L.) S. F. Gray. Willow-weed.
Aquatic; two collections on the Potomac flats between the Outlet Lock and Ead'fl Mill. Midsummer. Widely, distributee in N. Amer. (Polygonum hartwrightii A.
Gray; P. ampkibium L.)
2. Persicaria muhlenbergii (S. Wats.) Small.
River banks and other moist situations; not uncommon. Aug.-Scpt. Widely distributed in N. Amer. (Polygonum cmersum Britton; P. arnphibium terrestre of Ward's Flora; P. muhlenbergii S. Wats.)
3. Persicaria lapathifolia (L.) S. F. Gray. Willow-wehd, Low waste places; common, especially on the Potomac Flats. July-Sept. Through- out N. Amer. (Polygonum incarnalum Ell.; P. lapathifolium L.)
4. Persicaria pennsylvanica (L.) Small.
Wet places generally; common. July-Sept. Eastern N. Amer. (Polygonum pennsyIvanicum L.)
5. Persicaria hydropiper (L.) Opiz. Smartweed.
Law moist situations; locally common. July-Sept. Nearly throughout N. Amer.;
naturalized from Ear. (Polygonum hydropiper L.)
6. Persicaria punctata (Ell.) Small. , Smartweed.
Swamps and moist alluvial situations; common. July-Sept. Nearly throughout N. Amer. (Polygonum punctatum Ell,)
7. Persicaria orientalis (L.) Spach. Prince' s-feathbr.
Waste places; not uncommon, particularly along the Canal and on the Potomac Flats. July-Sept. Native of India; escaped from gardens and naturalized in the eastern U. S. (Polygonum onentale L.) .
8. Persicaria mitis Gilib. Lady's-thumb. Pinkweed.
Moist waste places; common, especially along the river. June-Sept. N. Amer.
and Eur. (Polygonum persicaria L.; Persicaria persicaria Small.)
9. Persicaria hydropipetoides (Michx.) Small.
Wet alluvial situations; several stations along the Potomac, but not common.
Aug.-Oct. N. Amer. (Polygonum hydropiperoides Michx.)
5. BILDERDYKIA Duin.
Plants annual; outer sepals keeled at maturity.... 1. B. convolvulus.
Plants perennial; outer sepals conspicuously winged at maturity...2. B. scandens.
I
FLORA OF THE DISTRICT OF COLUMBIA. 147
1. Bilderdykia convolvulus (L.) Dum. Bindweed.
Waste and cultivated ground; common weed. Summer. Naturalized from Eur.;
nearly throughout N. Amer. (Polyqonum convolvulus L.: Tiniaria convolvulus Webb & Moq.)
* t 2. Bilderdykia scandens (L.) Greene.
Thickets and brushy fields; abundant. July-Sept. Eastern N. Amer. {Poly- gonurn scandens L.; Tiniaria scandens Small.)
Polygonum cristatum Engelm. <& Gray is a form of this species with incised sepal wings. It has been collected at several localities within our range,
6. PLETTOOPTEBTTS Turcz.
1. Fleuropterus zuccarinii Small. Japanese knotweed.
Escaped from cultivation at several localities. July-Oct. Native of Japan; escaped locally in the northeastern IT. S. (Polygonum cuspidatum Sieb. <6 Zucc.'i
7. TRACAULON Raf, Tear-thumb.
Stems sharply 4-angled; leaves short-petioled, the blades arrow-shaped; style 3- parted; achene sharply 3-angled 1. T. sagittatum.
Stems ridged; leaves mostly long-petioled, the blades halberd-shaped; style 2-parted;
achene lenticular 2. T. arifolium.
X. Tiacanlon sagittatum (L.) Small.
Swamps, wet thickets, and stream banks; common. Aug.-Sept. Eastern X.
Amer. (Polygonum, sagitt.atuin L.)
2. Tracaulon arifolium (L.) Raf.
Low woods or borders of woods; not very common. A n r.-Sept. Eastern X.
Amer. (Pobjtjtmw.n arifolhttii L.)
8. FACtOPYETJM Gaertn. Buckwheat.
I. Fagopyrum esculentum Moench.
Dump1? and waste places; occasional. Summer. Cultivated in X. Amer.;
some times escaping. (F<tgo pyru ni /ago pyrum Karst.)
46. CHEJTOPODIACEAE. Goosefoot Family.
Leaves linear, pungent-tipped; plants neither mealy nor glandular 3. SALS OLA.
Leaves broader than linear, not pungent-tipped; plants glandular or more or less white-mealy.
Fruit inclosed in a regular toothed calyx; leaves all alternate; flowers all alike.
1. CHENOPODrUM.
Fruit inclosed by 2 nearly distinct triangular green bracts; lower leaves opposite;
flowers of 2 kinds, slaminate and pistillate 2. ATBIPLEX.