16 Sir J. F. W. Herschel on the Action of the Rays 
loped) are more sensitive than those produced eyen from the 
same plant, at a late period in its flowering, and have their 
colours more completely discharged by light. As the end of 
the flowering period comes on, not only the destruction of the 
colour by light is slower, but residual tints are Jeft which re- 
sist obstinately. A very remarkable case of this kind was no- 
ticed in Chryseis californica, the earliest flowers of which ex- 
hibited in the photograph of their spectrum a well-insulated 
round spot, eaten away by red rays almost at its extremity, 
which spot I never was able to reproduce with later flowers 
from the same root. Those gathered at the end of its flower- 
ing also left a residual yellow of extreme obstinacy*, which 
was by no means the case with the earlier flowers. 
174. It would be waste of time to enumerate all the vege- 
table tints which I have subjected to experiment, comprising 
most of the ordinary hardy garden and wild flowers of the 
country. ‘To the rarer and more splendid species which 
adorn the stoves and greenhouses of florists, I have had little 
access, a circumstance I much regret, and which leads me to 
take this opportunity of mentioning, that specimens of paper 
stained with the juices of highly-coloured, or otherwise remark- 
able flowers or leaves, either by alcoholic extraction, or by 
simple expression (if accompanied with the botanical name of 
the plant used), will be highly acceptable, from whatever 
quarter received. I shall here set down only those which af- 
forded some ground for special remark, so far as I have yet 
pushed the inquiry. 
Colours of particular Flowers. 
175. Corchorus Japonica.—The flowers of this common and 
hardy but highly ornamental plant, are of a fine yellow, some~ 
what inclining to orange, and this is also the colour the ex- 
pressed juice imparts to paper. As the flower begins to fade 
the petals whiten, an indication of their photographic sensi- 
bility, which is amply verified on exposure of the stained paper 
to sunshine. I have hitherto met with no vegetable colour so 
sensitive. Ifthe flowers be gathered in the height of their 
season, paper so coloured (which is of a very even and beauti- 
ful yellow) begins to discolour in ten or twelve minutes in clear 
sunshine, and in half an hour is completely whitened. The 
colour seems to resist the first impression of the light, as if 
by some remains of vitality, which being overcome, the tint 
gives way at once, and the discoloration when commenced 
* Probably, therefore, useful in dyeing. The species is that most com- 
monly cultivated in gardens, with bright yellow petals having orange-co- 
loured bases. 
