Cooler Tour: February 19 2018

Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles occur all over the plant – on the stem and flat parts of leaves. They are an adaptation that protects the plant from being eaten by herbivores. Typically, an involucre with a clasping shape of a cup or urn subtends each of a thistle’s flowerheads.

The term thistle is sometimes taken to mean exactly those plants in the tribe Cardueae (synonym: Cynareae),[1] especially the genera CarduusCirsium, and Onopordum.[2] However, plants outside this tribe are sometimes called thistles, and if this is done thistles would form a polyphyletic group.

A thistle is the floral emblem of Lorraine and Scotland, as well as the emblem of the Encyclopædia Britannica.

 

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