b TWINING PLANTS. Chap. L 



were at the same time revolving ; and this was the case 

 with most of the plants observed by me. With all, if in 

 fall health, two internodes revolved ; so that by the time 

 the lower one ceased to revolve, the one above was in 

 full action, with a terminal internode just commencing 

 to move. With Hoya carnosa, on the other hand, a 

 depending shoot, without any developed leaves, 32 

 inches in length, and consisting of seven internodes 

 (a minute terminal one, an inch in length, being 

 counted), continually, but slowly, swayed from side 

 to side in a semicircular course, with the extreme 

 internodes making complete revolutions. This sway- 

 ing movement was certainly due to the movement of 

 the lower internodes, which, however, had not force 

 sufficient to swing the whole shoot round the central 

 supporting stick. The case of another Asclepiadaceous 

 plant, viz., Ceropegia Gardnerii, is worth briefly giving. 

 I allowed the top to grow out almost horizontally to 

 the length of 31 inches ; this now consisted of three 

 long internodes, terminated by two short ones. The 

 whole revolved in a course opposed to the sun (the 

 reverse of that of the Hop), at rates between 5 hrs. 15 m. 

 and 6 hrs. 45 m. for each revolution. The extreme tip 

 thus made a circle of above 5 feet (or 62 inches) in dia- 

 meter and 16 feet in circumference, travelling at the 

 rate of 32 or 33 inches per hour. The weather being 

 hot, the plant was allowed to stand on my study-table ; 

 and it was an interesting spectacle to watch the long 

 shoot sweeping this grand cricle, night and day, in 

 search of some object round which to twine. 



