TWINING PLANTS 
By J. B. CLELAND 
Looked at from above, a twining plant 
may ascend clockwise or anti-clockwise. Or 
looked at from the front of its support, it 
may ascend by passing in front from right to 
left (clockwise), or left to right (anti-clock- 
wise) . 
Charles Darwin, in “The Movements and 
Habits of Climbing Plants,” 1876, says: — 
“A greater number of twiners revolve in a 
course opposed to that of the sun, or to the 
hands of a watch, than in the reversed 
course .... and ascend their supports from 
left to right.” (P. 33.) 
Darwin here makes the mistake of referring 
to the course of the sun. In the Northern 
Hemisphere (to which Darwin of course re- 
refers), if we take a runner bean (which 
twines anti-clockwise) on its support (a long 
pole) and look at the sun, the sun passes 
behind the pole from left to right but the 
bean passed behind from right to left (the 
sun moving south as it ascends). In the 
Southern Hemisphere, the sun moves north 
and so passes behind the pole from right to 
left, just as the twining bean does here. This 
seems an extraordinary mistake for Darwin 
to have made but he repeats it again and 
again on pages 24 to 31, referring to plants 
as moving against the sun or following the 
sun. Had he stuck to the hands of a watch, 
there would have been no ambiguity. 
Pain and Barkhill, in “Annals of Roy. 
Bot. Gardens, Calcutta,” XV Pt. 1., discuss 
the genus Dioscorea (true yams). The 
article deals with the species of this genus 
that occur in the East. Pt. 1 embraces those 
species which twine to the left (that is clock- 
wise). Presumably Part II deals with species 
that twine to the right. In Pt. 1, two species 
at least cross the line. If the twining follows 
the sun. what is the poor plant to do in the 
tropics, particularly at the erjuator? 
At first I failed to realise that Darwin, in 
speaking of “climbing plants,” meant those 
whose stems or branches ascend their support 
spirally and did not under this heading in- 
clude plants with tendrils such as the vine, 
passion-fruit and pumpkin. The latter he 
deals with in Chapters 3 and 4 under the 
heading of “Tendril-Bearers.” Darwin notes 
that some tendrils may reverse the direction 
of the twist and may do so several times. 
The four species of tendril-bearers in my 
garden show that the twining on the same 
plant may be clockwise or anti-clockwise and 
that reversal of twist may occur. The fol- 
lowing results were noted: — 
Grape vine. — Anti-clockwise 11, clockwise 
5. anti-clockwise and then clockwise 1. In a 
bifid tendril clasping a straw, one branch 
twisted one way and the other the reverse. 
Ordinary Passion- fruit. — Anti-clockwise 
15, clockwise 10. 
Banana Passion-fruit. — Anti-clockwise 10, 
clockwise 10, clockwise then anti-clockwise 
1 . 
Triamble (Pumpkin) .- — The tendril has 
three branches, two of which may twist in 
the same direction and the other in the re- 
verse. In one case, the central branch went 
clockwise below, then anti-clockwise, becom- 
ing bent back and turning round itself. Of 
six other tendril branches noted, three went 
one way and three the other. 
A colony of the Native Lilac ( Harden - 
bergia violacea ) near the Cherry Plantation 
in the National Park, all show an anti-clock- 
wise spiral of the twining stems. So far, I 
have not had the opportunity of observing 
other twining plants, especially native ones, 
but will make other observations when the 
chances occur. 
Tage Twenty-eight 
