180 D. P. Penhallow — Tendril Movements in 



tion of the axis, greatest increase in the weight of the squash, 

 and most rapid movement of the motile parts, during the hour3 

 between sunset and sunrise. 



From the experiments now under consideration, we find that 

 the growth during hours of darkness was in reality less than 

 that during daylight, since we obtained in the case of tendrils, 

 a movement of 1359-90 cm for the day, against 53690 0m for the 

 night; and in the growth of the vine, 44'44 cm for the day 

 against 34'28 cm for the night. Kauwenhoff found that the 

 growth in Cucurhita pepo for twelve hours of day, was 56*9 per 

 cent of the whole, thus leaving only 43 per cent for the same 

 number of hours of night, or a ratio of 1 : 1*32 in favor of the 

 former. Our own results are in striking confirmation of this, 

 si nee as already seen, our ratio is as 1 : 1*29 in favor of daylight. 

 In the case of the tendrils, the superior influence of conditions 

 during the day, becomes much more manifest. 



The movements of the tendrils are found to occur in well- 

 de fined waves of greater and less activity, which, usually longer 

 and of slower movement at the outset, are of decreasing length 

 and greater activity with advancing age up to a certain period. 

 This, however, is soon reached, and beyond this point the 

 movements become somewhat longer, but more especially 

 slower, with greater maturity. 



It is also important to note that the motion of the tendril is 

 always most rapid when accomplishing its grand sweeps 

 through the central region of the figure it describes, but that it 

 becomes slower and more intermittent when it reaches its ex- 

 treme lateral position on either side. This is often very mani- 

 fest in the figure obtained, but may be seen more clearly when 

 the waves of growth are plotted. This fact was noted by Dar- 

 win* as occurring in the Cucurbitaceoe, especially in Echinocystis, 

 but he does not appear to have gained a solution of its cause. 

 Nevertheless, there is every reason to believe that it originates 

 directly in the unequal torsion of the tendril arm, which would 

 of course be greatest at the extreme lateral range, and produce 

 the most variable action, while it would be least and give rise 

 to the most uniform and regular movement, when the tip 

 reaches the central region of its course. 



So long as all the tissues remain soft and in an actively grow- 

 ing condition, the waves of growth will succeed one another in 

 accordance with the controlling influences already spoken of, but 

 asthereisan advance in age with general hardening of the tissues 

 and large formation of wood, a noticeable and general length- 

 ening of the waves ensues. The tip may even drop toward 

 the ground as if exhausted and not resume its nutations for one 

 or even two hours. When it does, it is generally with a more 

 sluggish action. 



* Climbing Plants, p. 129-30. 



