74 MR. DARWIN ON CLIMBING PLANTS. 



Echinocystis lobata. — I made numerous observations on thia 

 plaut (raised from seed sent me by Prof. Asa Gray), for bere I 

 first observed the spontaneous revolving movement of tbe inter- 

 nodes and of tbe tendrils ; and knowing nothing of tbe nature of 

 tbese movements, was infinitely perplexed by the whole case, and 

 by the false appearance of twisting of tbe axis. My observations 

 may now be greatly condensed. I recorded thirty-five revolutions 

 of the internodes and tendrils ; the slowest rate was 2h., and the 

 average, with no great fluctuations, was lb. 40m. for each revolu- 

 tion. Sometimes I tied the internodes, so that the tendrils alone 

 moved ; at other times I cut off the tendrils whilst very young, so 

 that the internodes revolved by themselves ; but the rate was not 

 thus affected. The course generally pursued was with the sun, but 

 often in the opposite direction ; sometimes the movement during 

 a short time would either stop or be reversed ; and this apparently 

 resulted from the interference of the light, shortly after the plant 

 was placed close to a window. In one instance, an old tendril, 

 which had nearly ceased revolving, moved in one direction, whilst 

 the young tendril above moved in the opposite direction. The 

 two uppermost internodes alone revolve ; as the internodes grow 

 old, the upper part alone moves. The summit of the upper 

 internode made an ellipse or circle about 3 inches in diameter, 

 whilst the tip of the tendril swept a circle 15 or 16 inches in dia- 

 meter. During the revolving movement the internodes become 

 successively curved to all points of the compass ; and often in 

 one part of their course they were inclined, together with the 

 tendril, at about 45° to the horizon, and in another part stood 

 vertical. There was something in the appearance of the revolving 

 internodes which continually gave the false impression that their 

 movement was due to the weight of the long and spontaneously 

 revolving tendril; but, on suddenly cutting off the tendril with a 

 sharp scissors, the top of the shoot rose very little, and went on 

 revolving: this false appearance is apparently due to the inter- 

 nodes and tendrils all curving and moving harmoniously together. 



I repeatedly saw that the revolving tendril, though inclined 

 during the greater part of its course at an angle of about 45° 

 (in one case of only 37°) above the horizon, in one part of its 

 course stiffened and straightened itself from tip to base, and became 



modified flower-pcdunclcs, as is certainly the case with the tendrils of Passion- 

 flowers. Mr. E. Ilolland (Hardwicke's ' Science- Gossip,' 1865, p. 105) states 

 that " a cucumber grew, a few years ago, in my own garden, where one of the 

 short prickles upon the fruit had grown out into a long curled tendril." 



