228 Transactions of the Royal Microscopical Society. 
variegated mint, Begonia, Argyro stigma, &c., arise from the 
absence of chlorophyll in the cells subjacent to the epidermis at 
those parts, which produces the same effect as we see in leaves that 
have been mined by caterpillars. 
Now it follows that the colouring agent which is found in 
vegetables is in several states of combination; first, with the 
extractive principle; secondly, with the resinous principle ; and 
thirdly, with a starchy or gummy principle, and it is these states 
which indicate the means of extracting them. 
Firstly, when, as in the case of logwood, madder, &c., the 
receptacle of the colour is of the nature of extracts, water is 
capable of dissolving it. 
Secondly, certain of the resinous colouring matters are soluble 
in alcohol, spirits of wine, or ether, and form in many cases the 
pharmaceutical tinctures: the other principle will be left, as it is 
hardly in connection with our subject. 
We will take as a standard the two solutions of chlorophyll, 
viz. that in oil normal, and that also in oil acid. 
In chlorophyll No. 1 we have a spectrum made up of four 
bands, two of which are definite, and one shaded, while the other 
is a general absorption of the blue end. Compared with this, we 
have chlorophyll No. 2, or that to which a small quantity of acid 
has been added ; we find on examination that a general displacement 
towards the blue end has taken place, which result, as shown by 
Mr. Sorby,* is due to a true decomposition of the original sub- 
stance, obtained when acid is added,{ though it is not regained 
when the acid is neutralized, as the normal action has gone too far 
for subsequent recovery; a material transformation has, however, 
taken place in the whole spectrum, the bands are constant though 
displaced, while their ratios are almost identical; this will be more 
clearly seen on reference to Fig. 2. 
We deduce that the acid has transformed an original sub- 
stance, which had the power of absorbing the rays of light, beyond 
» 652°0; still another band is produced at » 662-0, and though 
the bands 2 and 8 are proportionately shifted towards the blue, 
and have likewise gained in intensity, the general absorption is 
constant, and has sustained no apparent change: does it not 
appear possible that, in the case of solutions contaiming more 
acidity, this general absorption might be carried still farther into 
the blue, as, for instance, in other of the colouring agents of plants ? 
and if so, then in the event of an alkaloid form being also present in 
combination, the same spectrum as Fig. 2 may be still maintained, 
while the general absorption, &c., will be more nearly approached 
* ‘Roy. Micro. Jour.’ vol. xiii. 
+ See Mr, Sorby’s paper “On Comparative Vegetable Chromatology,” ‘ Royal 
Society Proceedings,’ vol, xxi. p. 406, 
