OF MOVEMENT IN PLANTS. 69 
daylight, since, in the case of the tendrils, we obtained a movement of 1359.90 cm., for 
the day, against 536.90 for the night, and in the growth of the vine, 44.447 cm., for the 
day, against 34.287 for the night. 
Rauwenhoff found that the growth in Cucurbita pepo, for twelve hours of day, was 
56.9 p. c. of the whole, and only 43 p.c. for the same number of hours of night, thus 
giving a ratio 1: 1.32 in favor of the former. Our results in the growth of the vine 
are in somewhat striking confirmation of this, since, as seen, our ratio is as 1: 1.29 in 
favor of day light. In the case of the tendrils, the superior influence of conditions 
which obtain during the day becomes even more apparent. The one conclusion to be 
derived from these facts appears to be, that the superior influence of temperature in 
promoting growth overcomes the lesser and retarding influence which may be exerted 
by light. 
From our previous considerations, it is clear that the movement of the tendril is but 
a normal manifestation of growth, and therefore subject to the same influences as other 
vital phenomena. These movements have been found to occur in well defined 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. So long as all the tissues 
remain soft and in an actively growing condition, these waves will succeed one another 
in accordance with the controlling influence already spoken of. But as there is an 
advance in age with general hardening of the tissues and large formation of bast, a 
noticeable and general lengthening 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. 
GROWTH IN LENGTH.—From previous considerations, it is clear that most rapid 
elongation and most active movement in the tendril, are simultaneous and directly cor- 
related throughout the entire period of movement. It is, therefore, to this very rapid 
elongation in the first instance that we must look for a true explanation of the circum- 
nutation. On the other hand, the structure of the tendril, presenting, as it does, a 
diversity of tissues, at once points to the fact that this rapid extension cannot be partaken 
of by all the tissues in equal degree. The vascular elements are those in which the least 
extension can occur of all the tissues present. With reference to all the other tissues, 
therefore, they must be brought into a state of positive tension which continually 
increases in strength as age advances and the constituent cells become more strongly 
modified. In the collenchyma also, while capable of greater extension and variation of 
tension than the wood and bast cells, yet with reference to the unmodified fundamental 
structure in active growth, there must be a well-pronounced positive tension. This fact 
is at once demonstrated by the changes which follow the cutting of sections. Transverse 
sections quickly bulge out in the centre with a strong marginal contraction. Longitudinal 
sections show a strong curvature with the concavity on the side along which the collen- 
chyma lies. We may also, doubtless, ascribe a certain amount of this contraction to the 
effect of irritation, which causes a loss of water within the affected area, and thus, through 
condensation, a further increase of tension. This is essentially the view held by Sachs 
