Application of the Micro-spectroscope, &c. By Thos. Palmer. 231 
Perhaps the best example of a change in colour existing in the 
evergreen shrubs of our gardens and hedges, is holly ( Ilex aquifo- 
lium), the leaves of which plant have been found to be extraor- 
dinarily sensitive to light, the quantities of chlorophyll and orange 
xanthophylls varying as much as 40 to 50 per cent, from those in 
the interior of the plant, and so shaded from the direct action of 
the sun, and those which are always exposed to a southern aspect. 
The spectrum, which is not unlike that of Figs. 3 and 4, laurels in 
alcohol, &c., is given in Fig. 6, though in the case of laurel the 
general absorption is nearer the red, and the bands are all more or 
less darker and broader. Doubtless many of you have noticed that 
in the variegated species of this plant, the young leaves, when first 
developed, are of a pinkish tint, especially around the edges, which, 
when they become mature, are quite white, or rather a whitish 
yellow hue. This, without doubt, is another of the many changes 
effected by the action of light, for, when growing in an aspect 
protected from the direct action of the sun’s rays, these leaves take 
a considerably longer period to become like others that are exposed, 
even though they may be part of the same shrub. But such a 
cause as this is easily understood, when we recollect and consider 
that the production of chlorophyll itself is entirely due to the action 
of light, and we all must admit that Mr. Sorby has quite established 
that point in his admirable paper on comparative vegetable chro- 
matology, which has been so often before referred to, and which all 
who desire to thoroughly master this subject would do well to read 
most intently. 
Mr. Sorby there shows that leaves of Acuta japonica produced 
50 per cent, more chlorophyll, and 25 per cent, less xanthophyll 
when shaded, than those exposed, in the short period of three weeks. 
This, moreover, was performed on a leaf of nearly a year old, and 
it must not therefore be overlooked, that whereas the xanthophyll 
had diminished, the yellow substances soluble in water had increased 
100 per cent. After such a valuable addition to our knowledge of 
such matters, has been made by so able a worker as our worthy 
President, it is quite needless for me to say that I have arrived at 
precisely the same results with laurel, holly and other plants of the 
same species. I therefore can but form a similar conclusion, viz. 
that this difference should take place seems to prove, either that 
the action of shade is favourable to the development of chlorophyll, 
which would entirely disagree with all the hitherto well-known 
facts ; or else, that the increase in its amount does, in some measure, 
indicate the quantity formed also in the other, but decomposed in 
the same interval by exposure to the sun. At all events, the facts 
presented to us seem to prove that the equilibrium between the 
different constituents of leaves can soon be changed by altered con- 
ditions. It must, however, be especially remembered, that by thus 
