112 PROCEEDINGS OF THE ACADEMY OF [1899, 



tional fact being that the curving seemed to commence about 3 

 P.M., and to reach its maximum about 5 P.M. The stronger' 

 branches had the greatest curve, in some cases making a complete 

 circle, the point of the branchlet reaching the main stem, the 

 curve of the weaker branches usually reaching a half circle. On 

 the evening of the 7th I tied a light label weighing an eighth of 

 an ounce to the apex of one strongly curving bi'anchlet. It had 

 no result in weighing the branchlet further down. In the morning 

 it still held the branch down to the point I had left it the evening 

 before, though the point beyond the string had grown a little and 

 taken an upward curve. When I cut the string with the point of 

 a scissors, the branch flew upwards with a sudden spring, reducing 

 the curve from a half to the quarter of a circle. The stem retained 

 this light curve during the whole of its subsequent growth. In 

 this connection it may be noted that in the reflex from the curve to 

 erection in Helianthus orgyalis, the stem never reached a perfectly 

 straight line, and hence the stems of this species are generally 

 flexuose. That the curves in Palafoxia should be in any direction of 

 the compass indifferently, and yet in specified directions only in. the 

 two Helianths, is remarkable. 



While taking notes on these plants at dusk one evening, I noted 

 that a plant of Helenium autumnale, wuth hundreds of unopened 

 flowers, seemed drooping for want of water. Calling the fact to 

 the attention of Mr. Hemming, in charge of my hardy herba- 

 ceous department, he felt sure that it only needed water, and this 

 was copiously applied, with no result. Closer examination showed 

 that the common peduncle was bent in the middle, the upper por- 

 tion forming a right angle with the stem. So rigid was the bend 

 that they could not be straightened without injury. The angle is 

 maintained for a number of days till the ray florets become visi- 

 ble, when the peduncle gradually straightens, taking several days 

 to complete the task. As in the case of the Helianths, pins were 

 inserted in order to note any uncoiling process if present. The 

 straightening was done by a purely ascending process. 



The gain to science by these observations is negative. It is 

 clearly seen that what we have understood as heliotropism in con- 

 nection with plant movements has no place in the phenomena. It 

 may be assumed that we have to look to various phases of life- 

 energy in the plants themselves for the final explanation. 



