336 BARWmiANA. 



movement may be plainly seen ; indeed, we have seen 

 a quarter-circuit in a Passiflora sicyoides accomplished 

 in less than a minute, and the half -circuit in ten min- 

 utes ; but the other half (for a reason alluded to in the 

 next paragraph) takes a much longer time. Then, as 

 to the coiling upon contact, in the case first noticed in 

 this country,^ in the year 1858, which Mr. Darwin 

 mentions as having led him into this investigation, 

 the tendril of Sicyos was seen to coil within half a 

 minute after a stroke with the hand, and to make a 

 full turn or more within the next minute ; furnishing 

 ocular evidence that tendrils grasp and coil in virtue 

 of sensitiveness to contact, and, one would suppose, 

 negativing Sachs's recent hypothesis that all these 

 movements are owing " to rapid growth on the side 

 opposite to that which becomes concave " — a view to 

 which Mr. Darwin objects, but not so strongly as he 

 might. The tendril of this sort, on striking some fit- 

 ting object, quickly curls round and fiimly grasps it ; 

 then, after some hours, one side shortening or remain- 

 ing short in proportion to the other, it coils into a 

 spire, dragging the stem up to its support, and ena- 

 bling the next tendril above to secure a readier 

 hold. 



In revolving tendrils perhaps the most wonderful 

 adaptation is that by which they avoid attachment to, 

 or winding themselves upon, the ascending summit of 

 the stem that bears them. This they would inevitably 

 do if they continued their sweep horizontally. But 



* [A. Gray, in " Proceedings of the American Academy of Arts and 

 Sciences," vol. iv., p. 98 ; and American Journal of Science and the 

 Arts, March, 1859, p. 2*78.] 



