TRANSACTIONS OF THE SECTIONS. 
73 
On the Action of Light on Plants . By Professor Daubeny. 
Professor Daubeny reported the progress which he has made in 
his experiments on this subject since 1833, when he communicated 
the results obtained up to that time to the British Association at 
Cambridge. At that period he had ascertained that the quantity of 
carbonic acid decomposed by a plant was in proportion, not to the 
chemical or heating influence of the ray transmitted to it, but to its 
illuminating power: he has since found that the functions of ex¬ 
haling moisture by the leaves, and absorbing it by the roots, depend 
upon the same law; with this difference, however, that, provided 
some light be present, a body radiating much heat will serve as a 
substitute for one transmitting a greater degree of light. Thus, a 
solution of ammonio-sulphate of copper, which absorbs and conse¬ 
quently radiates much heat, is nearly as efficient in causing the ex¬ 
halation and absorption of moisture as glass, which transmits the 
entire spectrum; and in proof that this does not depend upon any 
peculiar power residing in the violet ray, water obscured by ink, so 
as to produce an equally feeble illuminating effect, was found, in 
consequence of the heat it radiated, to produce an equal degree of 
exhalation. Yet when the plant was covered over by opake bodies 
radiating much heat, the amount of moisture exhaled was very in¬ 
considerable. 
Professor Daubeny has employed, in his experiments on plants, 
the light emitted by balls of lime ignited by the oxy-hydrogen jet, 
but could not discover that it exerted any influence on the quantity 
of moisture exhaled by them. 
Observations on the Structure of Horizontal Branches of Coniferae* 
By William Nicol. 
In a paper on the structure of recent and fossil Conferee , inserted 
in Professor Jameson’s Philosophical Journal for January 1834-, the 
author gave an account of a very striking difference he had observed 
in the structure of the opposite sides of a piece of the wood of Taxo - 
diuni disticha. The pith was much nearer one side than the other, 
and the narrowest was of a paler colour than the broadest side. The 
narrow side showed the usual structure of the true Pines in all the 
three principal sections, but the broad side in the transverse sec¬ 
tion possessed a greater degree of solidity than the narrowest side, 
and in both the longitudinal sections the vessels were filled with de¬ 
cussating fibres, and the discs were not only more sparingly bestowed 
but were also smaller and more obscure than those occurring in the 
other side. At the time this wood was examined he did not know 
whether it was a portion of a stem or a branch. He has since as¬ 
certained that it was a horizontal branch, and it then became inter¬ 
esting to determine whether the difference of structures was peculiar 
to the piece of wood in question ; whether it occurred in both the 
stem and branches of Taxodium disticha ; whether it was peculiar 
