A SEED KEY TO COMMON WEEDS 347 



57. Malva moschata L. Musk Mallow. L., 1.8 — 3.2 mm. 

 W., 1.6 — 3. mm. C, fruit dark gray or brown appearing sil- 

 very because of numerous hairs, seeds resembling Malva ro- 

 tundifolia but lighter in color. S., short kidney-shaped or cir- 

 cular with a notch on one side and a space of apparently differ- 

 ent texture in the center. 0., common in fields and meadows. 

 Introduced from Europe. 



58. Hypericum, perforatum L. Common Saint John's Wort. 

 L.. .5 — 1.2 mm. W., .2 — .5 mm. C, dark brown, shining. S., 

 abruptly tapering or rounded at the ends; cylindrical; surface 

 covered with longitudinal rows of minute (about twenty in a 

 row), indented scales or rectangular markings. 0., very com- 

 mon and troublesome. Introduced from Europe. 



59. Oenothera biennis L. Common Evening Primrose. L., 

 1.1 — 2.2 mm. W.. .5 — 1.5 mm. C, brick red. S., very irreg- 

 ularly 4 — 6 sided, usually sharp angles and flat faces; angles 

 often winged; surface minutely ridged or wrinkled. 0., quite 

 common in pastures, common in timothy and found in clover. 

 Native. 



60. Carum Carvi L. Caraway. L., 2.8 — 4.4 mm. W., .7 — 

 1.4 mm. C., rich yellowish red with six lighter longitudinal 

 ridges. S., somewhat fusiform with one side slightly concave 

 and the other broadly convex ; with six longitudinal ridges. 

 0., not a bad weed, sometimes cultivated. Introduced from 

 Europe. 



61. Daucus Carota L. Wild Carrot. L., 1.5 — 4.8 mm. W., 

 .8 — 2. mm. C, light greenish brown with lighter stripes. S., 

 flattened hemispherical, oval, with a row of frail edges along 

 the acute edges and from two to five rows of still more frail 

 spines running from end to end on the convex surface ; very 

 variable in size and shape ; in commercial seeds the spines are 

 often rubbed off. 0., common in red clover and in imported 

 alfalfa seeds. Introduced from Europe and spreading rapidly. 



62. Asclepias syriaca L. Common Milkweed. L., 6. — 8. mm. 

 including the wing. W.. 3. — 4.2 mm., including the wing. 

 Thickness, .8 — 1.2 mm. C, light reddish brown. S., ovate, 

 much flattened ; the base abruptly truncate ; one side slightly 

 concave and bearing a slight keel in the center extending for 

 about one-half the length of the seed ; with minute appressed 

 hairs. 0.. troublesome in pastures. 



