A SEED KEY TO COMMON WEEDS 345 



groove extending from the hook back along the sides showing 

 the location of the cotyledons; winged around the margin; 

 broadest toward the apical end. ()., not a remarkably bad 

 weed but rather common. Native. 



44. PotentUla monspeliensis var norvegica L. Rydb. Cin- 

 quefoil, Five Finger. Length .6 — 1. mm. W. .6 — .9 mm. C, 

 light yellowish brown sometimes slightly shining. S., nearly 

 round except for a short straight area on one side; sometimes 

 flattened and Ions-shaped in cross section ; surface covered with 

 numerous forked ridges or wrinkles. 0., common in alsike 

 clover and in timothy. Introduced from Eurasia. 



45. Agrimania striata Michx. Tall Agrimony. Length of 

 fruit 5. — 10. mm. including the hooked prickles. W. 4. — 8. 

 mm. C, reddish brown. S., turbinate or top-shaped with a 

 crown of hooked prickles; lower part with, about fifteen longi- 

 tudinal flutings; fruit two-celled and two-seeded; the lower 

 part slightly hairy. 0.. not a bad weed. Introduced from 

 Eurasia. 



46. Trifolium pratense L. Red Clover. L. 1.5 — 2. mm. W. 

 1. — 1.4 mm. C, light yellowish to bluish brown. S., some- 

 what triangular to ovoid; flattened; scar near the center of 

 one edge: differs from Medicago I a patina in not having the 

 prominent elevation at the seat-. O. cultivated. See Hillman. 

 Introduced from Europe. 



47. Trifolium repens. L.. White Clover. L., .8 — 1.4 mm. 

 W., .8 — 1.1 mm. ('.. yellow to brownish red. S., somewhat 

 shield-shaped; flattened; with a groove extending for a short 

 distance from the straight or concave end; one end rounded. 

 0., cultivated. Introduced from Eurasia. 



48. Trifolium hyhridum h. Alsike Clover. I... .8 — ■ 1.6 mm. 

 W., .5 — 1.4 mm. C, dark yellowish green to black. Shape. 

 almost identical in shape with Trifolium repens differing from 

 it principally in the color. 0.. cultivated. Introduced from 

 Europe. 



49. Melilotus alba Desr. White Melilot or Sweet Clover. 

 L.j 2. — 2.4 mm. W., 1.2 — 1.5 mm. (.'.. dull greenish brown 

 to greenish yellow, usually quite light colored. S.. smooth and 

 very nearly truly elliptical, with a broad shallow notch near 

 one end; has a peculiarly sweet odor. 0., found in alfalfa, 

 and red clove)-. Introduced from Europe. 



