high, leaves ovate, deeply serrate, downy underneath; flower cluster large, otherwise like the preceding. In waste places from New England to Missouri.

Small Nettle (Urtica urens, L.).-An annual, but slightly urticating, eight to twelve inches high; leaves elliptical, glabrous, shorter than the petiole; pistillate and staminate flowers in the same cluster. In waste places near dwellings from New England to Texas.

Western Nettle (Urtica holosericea, Nutt.).-A tall, stout, more or less stinging perennial, finely and densely tomentose; leaves thick, oblong to obovate-lanceolate, on a short petiole, tomentose, especially the lower surface of the leaf; staminate flowers in loose panicles; pistillate flowers in denser and shorter panicles. Common in Utah and westward; strongly urticating.

Buckwheat Family (Polygonaceae).—Herbs, shrubs, or trees, with alternate or sometimes opposite, entire leaves, stems with swollen joints; stipules in the form of sheaths; flowers small, regular, perfect, dioecious, monoecious or polygamous; petals none; sepals often colored, petal-like, two to six-cleft or two to six-parted; stamens two to nine; ovary one-celled, bearing two to three styles or stigmas; fruit usually an achene, compound or three or four-angled or winged; embryo curved or straight. About 800 species of wide distribution. Contains the buckwheat, rhubarb, docks, etc.

Curled Dock (Rumex crispus, L.).-A smooth perennial, growing from three to four feet tall, with a long root; leaves lanceolate, acute, margins wavy and curled; bases of lower leaves somewhat truncate or inclined to be heart-shaped; flowers collected in dense whorls, which become extended or prolonged ́into racemes entirely leafless above or with few small leaves below; flower with eight sepals, the three outer herbaceous and leaflike, the three inner larger, somewhat curled and forming, after flowering, the valves of the fruit; fruit three-angled, each

valve bearing a seed. Found along roadsides and in meadows across the continent, and in Europe.

Pale Dock or Peach-leaved Dock (Rumex altissimus, L.). Closely allied to preceding; from two to six feet tall; leaves longer than those of R. crispus, oblong, lanceolate, acute, rather thick, and without the wavy curled margin of curled dock; flowering racemes long, spikelike, petioled, and nearly leafless; one of the three valves in fruit bears a conspicuous grain.

White Dock (Rumex mex

icanus, Meisn.). Lower growing than either of the preceding, being not more than three feet in height; white root; narrow lanceolate or linear leaves, the lowest sometimes oblong; flowers in crowded whorls, the pedicel much shorter than the fruiting calyx; one, two, or sometimes, all three of the valves of the achene bear each a conspicuous grain. Low grounds from New England to California.

VAR

Patience Dock (Rumex Patientia, L.).-A tall, glabrous perennial; lower leaves long petioled; dense fruiting Fig. 97a. Sour dock (Rumex panicles. In low and moist crispus). A troublesome weed in grounds from New England fields, meadows and along roadto Utah. The broad leaved sides. (Harrison and Lockhead.)

or bitter dock (R. obtusifo

lius, L.) is a glabrous perennial with erect stem; lower leaves oblong-lanceolate; open panicle; wings of fruit with few spreading, spiny teeth. Naturalized from Europe.

Sheep Sorrel (Rumex acetosella, L.).-Sheep sorrel is closely allied to the docks and is quite prevalent in many parts of the North. It is a low, smooth annual or perennial, usually the latter, growing from six to twelve inches tall, and coming from a horizontal, creeping root; stem erect; leaves narrow, eared, lanceolate (the upper linear); flowers terminate, jointed stalks or stems, and are small, with green calyx and exserted stamens. Common in pastures and clover fields, the seed being sometimes introduced as an impurity in clover seed. The plant is also spread by means of underground roots and stems.

There is a widely spread belief that the soil in which this plant occurs is sour, that is, is lacking in lime, and that the addition of lime will exterminate the weed; but this opinion is erroneous, since sheep sorrel is quite as common upon the calcareous soils of Wisconsin and eastern Minnesota as it is on the dry, sterile hills of Massachusetts and Iowa.

Knotweed or Dooryard Weed (Polygonum aviculare, L.). A slender annual, or more commonly, a perennial, with a prostrate or somewhat ascending stem from six to twelve inches long; leaves ovate, lanceolate or oblanceolate with a short petiole, smooth or sparingly hairy; stipules, called ochreæ, silvery, two-parted, later cut or fringed; flowers in axillary racemes from one to five; sepals green with five lobes; style short, three divided; achene striated, three-angled. A common weed throughout eastern North America to the Pacific coast. Introduced from Europe. Found in both Europe and Asia.

Related to P. aviculare, is the larger knotweed (P. erectum), a glabrous annual, with erect stem from eight to fourteen inches high; leaves oval or oblong, nearly sessile on short petioles; flowers one to two in the axils of the leaves; stamens six, occasionally five; style short; achene three-angled. Native from New England to On

tario and Manitoba, extending south to Tennessee and Arkansas, and west to the Great Basin in Utah.

Another ally of these is the bushy knotweed (P. ramossissimum), an annual with bright or yellowish green, smooth leaves, erect or ascending stem, generally branched, from two to three feet high; flowers several in axillary clusters, greenish, pedicellate, achenes exserted, shining, three-angled, reticulate, dull in color. Common in Manitoba, Dakotas, Maine and New Jersey to Missouri, New Mexico and California.

Muhlenberg's Smartweed or Marsh Smartweed (Polygonum Muhlenbergii (Meisn.) Watson).-A decumbent

or nearly erect perennial, with long underground rootstocks; grows from one to three feet tall; flowers bright rose color, arranged in spikes from one to three inches long. Extremely common in low grounds, especially in old lake beds and ponds, which, when drained and planted with corn, often grow up to this weed, in the North.

Lady's Thumb (Polygonum Persicaria, L.). A nearly smooth annual or

Fig. 98. Dooryard weed (Poly- biennial from twelve to gonum aviculare).

eighteen inches high;

leaves lanceolate, pointed and somewhat rough, often marked with a dark triangular spot near the middle; spikes differ from those on P. pennsylvanicum, in being on peduncles that are free from glands; spikes ovoid or oblong, dense, and erect; calyx colored; stamens generally six; styles two to three-cleft; achene smooth and

shining, sometimes triangular. Originally from Europe but becoming very common in waste places.

Water Pepper (P. Hydropiper) is much like P. Persicaria, but more slender and often decumbent. It has greenish flowers and slender, nodding spikes; achenes dull in color and the whole plant more or less acrid. Another water pepper or smartweed (P. hydropiperoides) is a

perennial, not acrid; with leaves narrowly lanceolate or oblong and small flesh-colored flowers in erect slender spikes; smooth achenes sharply triangular.

Common Bindweed or Wild Buckwheat (Polygonum Convolvulus, L.).-A smooth or scurfy annual with a trailing or twining stem, two to four feet long with naked sheaths; leaves hastate or pointed; flowers in axillary clusters or in interrupted racemes; greenish with slender pedicels; calyx five, rarely six-parted; stamens eight; style nearly entire, stigmas three; achene

Fig. 99. Smartweed. Lady's three-angled, dull blackish, thumb (Polygonum Persicaria). obovoid. Common in waste

places and especially in grain fields of the North throughout North America. Native also to Asia and Europe, probably introduced early with grains. Very commonly found with wheat and oats seed in the North.

Pennsylvania Smartweed (Polygonum pennsylvanicum, L.). This smartweed, sometimes called heart's ease, is common in low grounds and corn fields. Peduncles of flowers with glands.

Slender Smartweed (Polygonum lapathifolium, L.).—