28 
REPORT— 1847 * 
which, if not etiolated, were very deficient of greenness. This has several 
times occurred under a glass which cut off seventy-five per cent, of actiuisn, 
and admitted ninety-five per cent, of light. Again, behind a cobalt blue 
glass admitting eighty of actinism and not more than twenty jut cent, of light, 
plants have been quite as much etiolated. It is clear, therefore, that tie for¬ 
mation of cldorophyl is not directly dejjcndcnt ujK>n either light or actiubm 
regarded as isolated principles. 
In the greater number of niy experiments with the prismatic speclruni, 
the greening of the plant has comineuci'd over the space occupie<l by the 
green rays; and, under grt;<Mi glasses, which admitted all the rays above 
the orange ray, plants have invariably grown of a very green colour. The 
influence of the solar rays upon the green colouring matter of leaves removed 
by infusion and pressure, extends with tolerable uiiifonnity over every ray 
of the spectrum, from the red to the violet (Sir,Tohtj Her»che'l,‘Onlhe.\etion 
of the Uays of the Solar Spectrum on Vegetable Colcmrs,’ Phil. Trans., vol. 
cxx.xiii.). In this case the green colour is however de.Htroyrd, ami aru'ldy 
brown of the same character as the brown of the leaf in autumn, U prodoced. 
This change appears to bo due to tight rather than actinism, aud presents 
a curious contrast to the results on inorganic coinpoutids. Here we ap[>ear 
to have a deoxidation of tlie cblorophyl jiroduced by light—a process analo¬ 
gous to the decomposition of carbonic acid by the living plant It is difficult, 
however, to apply oxpcrinicrjts made with dead vegetable matter to matter 
possessing the principle of life. I am led to infer from the facts, that plant* 
■null grow of a pale green colour under the influence of strong light (as 
admitted through yellow glass), and also under the radiations which permeate 
deep blue glass (actinic), whilst the heat radiations which pass glass coloured 
with oxjde of gold, and very lightly smoked glass, have a constant ttnHeoey 
to produce a certain degree of ruddy browniiess, even in healthy green plants 
and that chlorophyl is not formed by the agency of cither of those principles 
alone, but that jt results from the combined influence of light mid actinism. 
'“‘‘do with media which cut olF the heat rays, but which 
actinic rays, the plants grow of a lively green; and 
thin nnrt thcif Icavcs w presorvcd without change much longer 
of t!.P £ “7 «OQditiou8. To produce chlorophyl, a recombinalioii 
thc airl T"'^'"^ Jtghi ,u«ists the plant to s<.paratc from the water and 
fullv ’ ^ have little doubt but long-continued and care* 
combined 'T'" »»'''' chlorophyl results from the 
functions of n W ^ “cbnism in exciting one of those mysterious 
eCrg:Xhytlo8Ur''“ "" el„.l..hcouri»i.j,of 
I have nrevJftu,ili- *i._i *, . . ^ 
rvdark .,!« *^1 '"“uiih.c, unaor intense yellow, u^^tf 
to^there 77''' '"“y 7“ 
tive functions. This evidentlv nr! exertion of their reproduc- 
the chemical actions w-lunh H ^ necessity of some cheek upon 
the elements in the furmatinn^^ r” cctinism, and which c.xhaust 
the species. IJv removinn' nln,,* ^ which go to the proaervatiou uf 
flueiices of isolated licht or ant'n' * ^ 1‘ualthy condition from the in* 
to the ettocis of tholi?bont rm? r 1 "-here they may be expo^ 
«owers and seeVt leastVcfiigibleS, 
not an eflect of heut 
