12 PHILOSOPHICAL TRANSACTIONS. [anNO 1785. 



shaded from the sun, wind, rain, or any disturbing cause, the appearance of the 

 leaves is different from that of other pinnated plants. In the last a great uni- 

 formity subsists in the respective position of the leaves on the pinna ; but here 

 some will be seen on the horizontal plane, some raised above it, and others fallen 

 under it ; and in about an hour, without any order or regularity, which I could 

 observe, all these will have changed their respective positions. I have seen a leaf, 

 which was high up, fall down ; this it did as quickly as if a strong impression 

 had been made on it, but there was no cause to be perceived. Cutting the bark 

 of the branch down to the wood, and even separating it about the space of half 

 an inch all round, so as to stop all communication by the vessels of the bark, 

 does not for the first day affect the leaves, either in their position or their apti- 

 tude for motion. In a branch, which I cut through in such a manner as to 

 leave it suspended only by a little of the bark no thicker than a thread, the leaves 

 next day did not rise so high as the others ; but they were green and fresh, and, 

 on being touched, moved, but in a much less degree than formerly. 



After sun-set the leaves go to sleep, first moving down so as to touch each 

 other by their under sides ; they therefore perform rather more extensive motion 

 at night of themselves than they can be made to do in the day-time by external 

 impressions. With a convex lens I have collected the rays of the sun on a leaf, 

 so as to burn a hole in it, without occasioning any motion. But when the expe- 

 riment is tried on the petiolus, the motion is as quick as if from strong percus- 

 sion, though the rays were not so much concentrated as to cause pain when 

 applied in the same degree on the back of the hand ; nor had the texture of the 

 petiolus been any ways changed by this ; for next day it could not be distinguished, 

 either by its appearance or moving power, from those on which no experiment 

 had been made. The leaves move very fast from the electrical shock, even 

 though a very gentle one ; but the state of the atmosphere was so unfavourable 

 for experiments of this kind, that I could not pursue them so far as I wished. 



There are 2 other plants mentioned as species of this genus by Linneus. The 

 first, the averrhoa bilimbi, I have not had an opportunity of seeing. The other, 

 or averrhoa acida, does not seem to belong to the same class ; nor do its leaves 

 possess any of the moving properties of the carambola. Linneus's generic de- 

 scription of the averrhoa, as of many other plants in this country which he had 

 not an opportunity of seeing fresh, is not altogether accurate. The petals are 

 connected by the lower part of the lamina, and in this way they fall off while 

 the ungues are quite distinct. The stamina are in 5 pairs, placed in the angles 

 of the germen. Of each pair only one stamen is fertile, or furnished with an 

 anthera. The filaments are curved, adapted to the shape of the germen. They 

 may be pressed down gently, so as to remain ; and then, when moved a little 

 upwards, rise with a spring. The fertile are twice the length of those destitute 

 of antherae. — Calcutta, Nov. 23, 1783. 



