11/ V 



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PRAIRIE DOCK 



Silphium terebinthinaceum Jacq. 



July - August As (listiiictive as the lieiiu'iulous wands of flowers 



Prairie roadsides which iimrk the presence of rosin weed are the tall 



stalks of the prairie dock wliich rise above great 

 spade-sha])ed leaves. The leaves themselves are individuals; there is 

 nothing else like them in prairie, swamp, or forest. 



Prairie dock leaves come up in spring and stand without flower stalks 

 or further growth until August. The leaves are a foot or more long, on 

 stalks of shorter length, and arc thick, resinous, sjiadc-shaped, and 

 coarsely toothed. These leaves, like those of other Silitliiums aud plants 

 which, like these, live in hot. open sunshine and wind, are coated with a 

 rouffh waxv laver and are constructed in sueh a manner that moisture is 

 not easily evaporated from them. In the hottest weather the leaves do 

 not wilt. They are ereet above the ground and thus present only their 

 thin edges to the sun, not tlu' i)road faces of the leaves as the water lilies 

 and lotuses do. 



In August, from among the clusters of leaves, there spring tall, 

 smooth stalks, at the top of which are less than a dozen .smooth round 

 buds. These open as small sunflower.-*, very much like those of rosin weed, 

 but smaller and more delicate. High above the large leaves, these grace- 

 ful stalks seem to have no connection with the leaves or roots. Up in 

 the sunshine and against the prairie sky, the flowers of prairie dock wave 

 in the wind, bloom and go. The resin in the leaves and stems has an 

 odor suggestive of turpentine, hence the Latin name "ter<;binthinaceum". 



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