A SEED KEY TO COMMON WEEDS 353 



96. Achillea Millefolium L. Yarrow, Milfoil, L., 1.8—2.5 mm. 

 W., .7 — 1. mm. C, grayish flecked with darker spots. S., flattened 

 obovoid, sometimes curved : apex abruptly contracted and bear- 

 ing a tubercle ; surface with numerous very fine longitudinal 

 striations. 0., rather common in grass seeds. Introduced from 

 Europe. 



97. Anthem is Cotula L. May-weed, Dog Fennel. L., 1.2 — 2. 

 mm. W., .5 — 1.5 mm. C, light brown or dark straw-colored. 

 or brown. S., obovoid with about ten ribs composed of tubercle- 

 like projections ; base tapering into a cone-shaped structure ; 

 with a small tubercle at the apical end. 0., very common, es- 

 pecially in timothy, blue-grass and clover seeds. Introduced 

 from Europe. 



98. Anthemis arvensis L. Corn Chamomile. L., 1.4 — 2.5 

 mm. W., .5 — 1.5 mm. C., light brown or dark straw-colored. 

 S., somewhat four-angled or rounded in cross section ; apex trun- 

 cate and concave; base with a rounded knob; with about nine 

 rounded ridges on the sides. C, quite common in clover seeds. 

 Introduced from Europe. 



99. Chrysanthemum LeucantJiemum L. Ox-eye or White 

 Daisy, White Weed. L., 1.5—2.4 mm. W., .6 — 1.1 mm. C, dark 

 background with about ten heavy white ridges giving the whole a 

 light appearance. S., obovate with ten longitudinal ridges slight- 

 ly broader at apical end. 0., frequent but not abundant in 

 clover and small grass seeds. Introduced from Europe. 



100. Tussilago Farfara L. Colt's Foot. L., 3.2—4 mm. W., .4 

 — .6 mm. C, dark gray, appearing silvery because of the covering 

 of gray hairs. S., narrowly spindle-shaped; more attenuate at 

 the apex than at the base; with about six rows of long hairs 

 pointing towards the apical end; circular in cross section. 0., 

 not a bad weed but very common in certain places. Introduced 

 from Europe. 



101. Erecht'ites hieracifolia (L.) Raf. Fireweed. L., 2. — 3.1 

 mm. W., .3 — .5 mm. C, dark brown with lighter markings. 

 S., spindle-shaped with ten vertical light-colored ridges between 

 which are minute appressed white hairs ; expanded slightly at 

 the extreme apex. C, common in certain regions. Native. 



102. Senecio vulgaris L. Common Groundsel, Rag-wort, 

 Squaw-weed. L., 2.4 — 3.6 mm. W., .2 — .5 mm. C, light straw- 

 colored with vertical rows of white ascending hairs. S., clavate 



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