238 Field, Forest, and Wayside Flowers 
“The first purpose of the spontaneous revolv- 
ing movement,” says Darwin, ‘‘is to enable the 
shoot to find its support. This is admirably ef- 
Bind-weed (Convolvulus). Hop-vine (Humulus Lupulus). 
Twining “ against the sun.” wining “ with the sun.” 
Fic. 66.—Bind-weed and hop-vine. 
(From the Vegetable World.) 
fected by the revolutions carried on night and 
day, a wider and wider circle being swept as the 
shoot increases in length. This movement like- 
