88 MR. DABAVIN ON CLIMBING PLA^^TS. 



in 3 h. 12 m. ; in a second plant the same course ^vas followed, and 

 the two were completed in 3 h. 41 m. ; in a third plant the inter- 

 nodes followed the sun, and made two circles in 3h. 47 m. The 

 average rate of these six revolutions was 1 h. 46 m. The stem 

 shows no tendency to twine spirally round a support ; but the 

 allied tendril-bearing genus Paullinia is said (Mohl, S. 4) to be a 

 twiner. By the revolving movement, the flower-peduncles, which 

 stand up above the end of the shoot, are carried round and round ; 

 but when the intemodes were securely tied, the long and thm 

 peduncles themselves were seen to be in continued and sometimes 

 rapid movement from side to side. They swept a wide space, but 

 only occasionally moved in a moderately regular elliptical course. 

 By these combined movements one of the two short hooked ten- 

 drils, sooner or later, catches hold of some twig or branch, and 

 then it curls round and securely grasps it. These tendrils are, 

 however, but slightly sensitive ; for by rubbing their imder sur- 

 faces only a slight movement was slowly produced. I hooked a 

 tendril on to a twig ; and in 1 h, 45 m, it had curved considerably 

 inwards ; in 2 h, 30 m. it formed a ring ; and in from 5 to 6 hours 

 from being first hooked, it closely grasped the stick. A second 

 tendril acted at nearly the same rate; but I observed one that 

 took 24 hours before it curled twice round a thin twig. Tendrils 

 which have caught nothing spontaneously curl, after the interval 

 of several days, closely up into a helix. Those which have curled 

 roimd some object soon become a little thicker and tougher. The 

 long and thin main peduncle, though spontaneously moving, is 

 not sensitive and never clasps a support. It never contracts 

 spirally. Such contraction would apparently have been of service 

 to the plant in climbing ; nevertheless it climbs pretty well with- 

 out this aid. The seed-capsules, though light, are of enormous 

 size (hence its English name of Balloon- vine), and as two or three 

 are carried on the same peduncle, the tendrils arising close to 

 them may possibly be of service in preventing these balloons from 

 being dashed to pieces by the wind. In the hothouse they served 

 simply for climbing. 



The position of the tendrils alone suffices to show their homo- 

 logical nature ; but in two instances one of the tendrils produced 

 at its tip a flower ; this, however, did not prevent the tendril act- 

 ing properly and curling round a twig. In a third case the two 

 lateral branches which ought to have existed as tendrils,* both 

 produced flowers like the central branch, and had quite lost theii' 

 tendril-structure. 



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