spikelets chestnut colored, 3-flowered; the 2 lower flowers staminate with 3 stamens; the upper flower perfect, short pedicelled, awnless, with 2 stamens.

Distribution.-Common in the north. Frequently a troublesome weed in Minnesota and northwest territory. Common only as a weed in a few of the northwestern counties of Iowa.

Extermination. This weed can be exterminated by giving a shallow plowing after the crop has been removed and stirring the soil thus exposing the root-stocks to the action of the sun.

Poverty Grass (Aristida dichotoma Michx.).

Description. A slender, tufted, branched annual from 12-24 inches tall; spikelets in narrow, striate, simple or compound spikes;

FIG. 15.

Poverty Grass

(Aristida dichotoma). Common in dry, sterile soil. a, lower or empty glumes of a spikelet; b, a floret showing awns, middle one coiled.

empty glumes nearly equal, longer than the flowering glume, equaling the small lateral awns; the awns unequal, the long middle awn horizontal, but soon becoming reflexed.

Distribution.-Poverty grass is common in dry, sterile, or clay soil in southeastern Iowa.

Extermination.-The fibrous roots of the plant are easily killed by cultivation.

Long-awned Poverty Grass (Aristida tuberculosa Nutt.).

Description.-A rigid, much-branched perennial, 12-18 in. tall; panicles simple, 4-7 in. long; erect, rather distant branches, the lower in pairs of which one is short and few-flowered, the other elongated and many-flowered; empty glumes, nearly equal, awnpointed, flowering glume, twisted above to division of awns; awns nearly equal, articulated with glume.

Distribution.-Common gravelly knolls and sandy soil, northern and eastern Iowa.

Extermination.-Succumbs readily to cultivation.

FIG. 15-B. Poverty Grass (Aristida tuberculosa).

sandy fields.

(Photographed by Colburn.)

Common in gravelly and

Nimble Will (Muhlenbergia schreberi J. F. Gmel.).

Description.-A low, ascending perennial with slender, muchbranched, wiry culms, 1-2 ft. long; sheaths smooth, pilose at the throat; ligule very short; leaf-blade 1-2 lines wide, 1-4 in. long, scabrous on both sides; panicles 3-7 in. long, slender, branches erect, rather densely flowered; spikelets 1 line long, equaling or exceeding the pedicels; empty glumes minute, unequal, the lower sometimes obsolete; flowering glume narrowly lanceolate, pilose near the base, scabrous on the nerves above, terminating in a slender straight awn, 1-2 lines long; palea equaling the glume. Shaded thickets.

FIG. 16. Nimble Will (Muhlenbergia schreberi); a, sheath and base of leaf; b, d, glumes; c, lower part of rachilla; e, flower. In southern Iowa.

Distribution.-Nimble Will was originally confined to southeastern Iowa. It has spread northward along the Mississippi, where it is now abundant as far north as Dubuque. It occurs also in central Iowa in Story, Boone and Webster counties and is spreading. The grass is of little economic importance.

Extermination.-This weed is much more difficult to destroy than the other nimble weeds illustrated. The root-stocks spread more or less horizontally and are large and fibrous. Give a thorough cultivation, exposing the roots to the sun, and then follow with some leguminous crop. This weed is apt to be abundant in pastures. Here there is no other method of treatment than to get blue grass and white clover into the pasture.

Mexican Drop-seed Grass (Muhlenbergia mexicana (L.) Trin.).

Description.-An upright or ascending, usually much-branched perennial 1-3 ft. high, with a scaly, creeping root-stock; numerous flat leaves and contracted, densely-flowered panicles; sheaths longer or shorter than the internodes, smooth; ligule 12 line or less long; leaf-blades 1-3 lines wide, 2-7 inches long; spikelets about 1 line long on very short pedicels; empty glumes nearly equal, acuminatepointed about the length of the floral glume (a little shorter or sometimes a little longer), scabrous on the keel; flowering glume lanceolate, acute or mucronate-pointed, 3-nerved, pilose near the base and on the callus; palea a little shorter than its glume, very

acute.

Distribution.-Widely distributed in eastern North America, from Canada to Minnesota, South Dakota, Iowa, Nebraska and Missouri. Common everywhere in waste ground in Iowa, especially in Polk, Story, Pottawattamie, Webster, Crawford, Black Hawk, Calhoun, Clinton, Linn, Jasper, Lee and Dubuque counties.

Extermination. The character of the "roots" is so different from that of the roots of quack grass and the other perennial weeds that it is not difficult to exterminate. The "roots" of this weed and the allied species are more or less clustered. In an experiment conducted to exterminate it we found that by giving a shallow plowing of four or five inches and harrowing to expose the "roots" to the sun, they were killed, no growth making its appearance during the rest of the season. Of course this is not effective during rainy

weather.