This section is from the book "The Commonly Occurring Wild Plants Of Canada", by Henry Byron Spotton. Also available from Amazon: The Commonly Occurring Wild Plants Of Canada.
Herbs with the flowers in heads, surrounded by a many-leaved involucre, as in the next Family, but the stamens are distinct. Leaves opposite. Represented in Canada by the genus Tourn. Teasel. D. sylves'tris, Mill. (Wild Teasel.) A stout, coarse, prickly plant, not unlike a thistle in appearance. Flowers in oblong very dense heads, bluish. Corolla 4-cleft. Stamens 4, on the corolla. Bracts among the flowers terminating in a long awn. Leaves generally connate. - Roadsides and ditches. Very common in the Niagara district, but found also elsewhere.
 
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