230 Transactions of the Royal Microscopical Society. 
In the former specimen, which is prepared in ether, we have 
almost a facsimile of Fig. 2, though band No. 4 has disappeared ; 
where it began however, a general absorption is evident, bands 1 
and 2 are brought nearer the blue end, while No. 3 is farther from 
it. The spectrum from the petals of blue Cineraria, Fig. 4, is 
perhaps more striking, as the bands are all nearer the blue end, 
while their symmetry with the preceding spectra is considerably 
altered, still owing, no doubt, to the presence of an acid, though 
comparison is hardly admissible, as the former specimens are 
prepared from the green leaves, while the latter is extracted from 
the blue petals of the flower. 
We will now pass on to consider the spectrum of Shumac. This 
substance contains a considerable percentage of tannic acid ; Mul- 
ligan and Downing give 24°37 per cent. Having procured some 
of the leaves of this plant from Palermo, I pulverized them, and 
after due preparation the following solution in oil was the result ; 
the spectrum, which will be seen on reference to Fig. 5, 18 
curious enough to attract our notice, inasmuch as it almost agrees 
with Fig. 2, though the bands are all more or less nearer the 
blue end, yet the general absorption is increased towards the red. 
In this case we have a distinct proof of an existing acid in con- 
nection with the fluid; still there are differences, though to a less 
extent than in the previously considered specimens; may we not 
assume from this that the chlorophyll in the case of specimens 
Nos. 3 and 5 is in combination with some alkaline base, while the 
colour which is predominant in the case of No. 4, is of an acid 
construction? At the same time I must acknowledge there is 
every reason to think that an alkaline form is also present, though 
to a much less extent. It must, however, be borne in mind that 
this solution of Shumac is prepared from the dried leaves, and 
therefore I doubt whether the spectrum from living leaves would 
not be rather different from the one I have brought before your 
notice. 
Fic. 5.—SHumac. 
M. A. Observations. 
1 | 23°857 | Centre .. .. | 661-0 Class 1. Very black; size °485. 
2 | 22°60 _ sey ae | 0000 » 1. Centre shaded, ends very 
shaded ; size *20. 
SWOT Bad, San ee ees DoOND 5, 1. Indistinct; size °3. 
4 | 20-005 is .. .. | 5385°0 | Same as band No. 2; size 33. 
5 | 20°465 | Commencement | 517°0 | Very black; general absorption. 
But before leaving a subject which appears of some importance, 
there is one more solution, that of Tradescantia, Fig. 6, which is 
well worthy of our attention, as I think it bears especially on a 
