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teen inches long, deeply pinnatifid, the divisions frequently divided, prickly toothed, the upper surface smoothish and the lower white and woolly, finely divided stem leaves; single heads one and one-half inches long with purple flowers terminating the branches; bracts of the involucre somewhat appressed, slightly weblike; lower bracts ovate with a broad base and a weak, prickly, recurved bristle, slight dorsal gland; inner bracts, linear-lanceolate, with an entire, nearly colorless appendage; flowers purple, the lobes terminating in cleft tips; anther tips acute, filament pubescent;

[graphic]

bristles

pappus plumose, achene smooth, upper part yellow. On roadsides and in meadows from New Brunswick westward to Ontario, Minnesota and Iowa.

Canada Thistle (Cirsium arvense, (L.) Scop.).-A smooth perennial, spreading by creeping rootstocks; corymbosely branched at the top, growing one to three feet high, smooth; leaves lanceolate, sessile, and Fig. 158. Bull thistle (Cirsium lanceolatum). Com- deeply pinnatifid, the lobes and mon in pasture, wood lots margins of the leaves being beand roadsides. (Ada Hay- set with spiny teeth; heads small, three-fourths to one inch high, bracts pressed closely to head, the outer with a broad base, the inner narrow, all with an acute, never spiny tip; flowers purple, dioecious; all the bristles of the pappus plumose.

den.)

The chief points of difference between the Canada thistle and other allied species are as follows: the head is smaller, the involucre or modified leaves surrounding the head is not spiny, but smooth; the leaves are lance

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shaped, sessile and deeply divided, the lobes and margins having spiny teeth. Naturalized from Europe. Canada westward and southwest.

Knapweed (Centurea solstitialis, L.).—An erect, branched, annual with cottony winged stem, lower leaves lyrate, upper linear entire, decurrent; spines of upper bracts long spreading with a few smaller ones at the base; flowers yellow, pappus soft.

It is found in fields in the east and south of England, rare; it has been introduced with alfalfa, etc., into the United States.

Black Knapweed (Centaurea nigra, L.).—It is a scabrous perennial, with stiff, branched stems, lower leaves spatulate, dentate or lobed, upper leaves oblong or lanceolate, sessile or partly clasping; the bracts of the involucre are tipped with a fimbriate appendage; flowers are rosepurple; achenes four-sided. It is found on the Atlantic coast. The brown knapweed (C. Jacea) is a perennial, much like the preceding, with entire or denticulate leaves, globular involucre, brown bracts with fimbriate appendages, achenes four-angled. It appears in the East and Northwest on the Pacific coast. Star thistle (C. Calcitrapa) is an annual with pinnatifid leaves, outer bracts of the involucre ovate-oblong, each tipped with a stout spine; flowers purple; achenes compound, obscurely foursided. It appears on the Atlantic coast and in the Pacific northwest, but is native to Europe.

Blue Bottle, Bachelor's Button (Centaurea Cyanus, L.). -A branched annual from one to one and one-half feet high, woolly, tomentose; leaves linear, entire, the lower dentate or pinnatifid; heads many-flowered on long peduncles, involucre ovoid or globose; bracts imbricated, greenish yellow; flowers blue or purplish, varying to white; all tubular, the marginal one neutral, achenes compressed or four-angled; bristles of the pappus un

equal; native to Europe, frequently escaped from cultivation in the northern states, but sometimes cultivated as an ornamental plant.

Chicory or Succory (Cichorium Intybus, L.).— A branching perennial with deep roots and alternate leaves; basal leaves spreading on the ground; stem leaves oblong or lanceolate, partly clasping; showy flowers, bright blue, varying in pink or purple. Common along roadsides, in fields. and waste places from New England to Canada and Nebraska; especially common where chicory has been cultivated. A troublesome weed in Wisconsin and Minnesota. Allied to endive which is cultivated as a salad plant.

Long-rooted Cat's-ear or Gosmore (Hypochaeris radicata, L.). — Stems several, from a perennial root, slender, one to two feet high; branched or rarely simple, bearing a few scales; leaves oblanceolate to obovate in outline, pinnatifid-lobed to dentate, two to six inches long, hirsute on both sides; involucre about an inch long, glabrous or sparingly pubescent; achenes rough, all with very slender beaks longer than the body. Waste Fig. 160. Cat's ear (Hypochaeris radiplaces, western Washington to Cali- cata). (C. M. King.) fornia. Naturalized from Europe.

Skeleton Weed or Gum Succory (Chondrilla juncea, L.). A perennial with widely branching stems, one to three feet high, bristly hairy below, smooth above; basal leaves runcinate, pinnatifid; stem leaves few, linear heads few-flowered, short peduncled; involucre glabrous; achenes terete with an abrupt, slender beak, several ribbed, smooth below. Common eastward in fields and waste places. Native to Europe.

Dandelion (Taraxacum officinale, Weber.).—A smooth, or, at first, pubescent perennial; head many-flowered borne on a slender, hollow scape; root-leaves pinnatifid or runcinate; involucre double, the outer of short scales, the inner long, linear, erect in a single row, but closing after flowering; fruit ripens close to ground, the hollow scape elongating, the whole involucre then becoming reflexed, thus permitting the wind to scatter the "seeds;" achenes ("seeds") oblong, long beaked, the beak two or three times as long as the remainder of the achene, bear

ing at the end long, soft,
white capillary threads,
the pappus. Probably
native northward, but in
the southern states natu-
ralized from Europe.
Common also in Asia; a
cosmopolitan weed. Al-
lied to the above species
is a red seeded dandelion
which is not uncommon
in eastern North Amer-
ica. It is very much like
the
common dandelion
but has narrow "seeds"
that are a bright red or
red brown color; pappus
a dirty white.

Field Sow Thistle (Sonchus arvensis, L.). A

Fig. 160a. Common sow thistle glabrous perennial, pro(Sonchus oleraceus). (Ada Hay- ducing deep creeping den.)

rootstock, stem leafy,

branched, basal leaves runcinate-pinnatifid, spiny toothed, clasping by a heart-shaped base; flowers yellow; achenes transversely wrinkled. Common in the eastern

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