TWINERS AND CLIMBERS. 191 



instance has been recorded in another plant. This 

 was Ceropegia Gardneri, a tropical Asclepiad. The 

 top was allowed to grow out almost horizontally to 

 the length of 31 inches. This shoot had three long 

 internodes terminated by three shorter ones. The 

 whole shoot revolved in a direction opposite to the 

 course of the sun, and therefore in a contrary direc- 

 tion to the hop, occupying from five hours and a 

 quarter to six hours and three quarters in each revo- 

 lution. On account of the great length of this shoot 

 the circle through which it moved was about 5 feet 

 in diameter, or 16 feet in circumference, and the apex 

 travelled through this circle at the rate of 32 or 

 33 inches per hour. " The weather being hot," Mr. 

 Darwin writes, " the plant was allowed to stand on 

 my study-table ; and it was an interesting spectacle 

 to watch the long shoot sweeping this grand circle, 

 night and day, in search of some object round which 

 to twine." 1 



The greater number of twining plants climb in a 

 direction opposed to the course of the sun. The hop 

 and the bryony pursue the same course as the sun. 

 The bean (Phaseolus vulgaris), purple convolvulus, 

 and great white convolvulus, follow a course opposed 

 to the sun. The bitter-sweet (Solatium dulcamara), 

 which is a poor climber, turns in both directions. Of 



1 Darwin, " Movements of Climbing Plants," p. 6. 



