125 
1889—90.] Mr C. Michie Smith on Absorption Spectra. 
“ blue chlorophyll ” of Sorhy, or one, perhaps both, of the green 
chlorophylls of Stokes, is absent from the trichosanthes colouring 
matter. Its place is taken by another substance which yields the 
first band, which is not coincident with any of the chlorophyll 
bands. This substance, unlike that yielding the first chlorophyll 
band, is very readily decomposed by acids, and is slowly decom- 
posed by ammonia sulphide. 
Bands II., III., and V. in the trichosanthes spectrum apparently 
coincide in position with bands III., IV., and V. of the chlorophyll 
spectrum. Of these latter III. and V. are not distinctly shown in 
the accompanying plate, but are obtained with a comparatively weak 
solution and a strong light. Band IV. of the trichosanthes spectrum 
is extremely faint. It is not, however, possible to lay much stress 
on the apparent coincidence of these bands, since their behaviour 
under treatment with ammonia sulphide is so very different. A 
comparison of spectra ( g ) and ( h ) shows that no two of the bands 
are even approximately coincident — in fact, the two spectra are almost 
complementary. On the other hand, spectra (?') and (j) show that 
after treatment with strong hydrochloric acid, there is almost perfect 
coincidence between three of the bands in the two spectra. The 
influence of hydrochloric acid on chlorophyll has been studied by 
many observers. Russell and Lapraik * consider that the change 
produced is simply a molecular one, and call the two forms a- and 
/2-chlorophyll. Schunck, on the other hand, holds f that the change 
is a chemical one, and that the ultimate product is identical with 
Fremy’s phyllocyanin. The latter view certainly seems to explain 
the observations best, and in accordance with it we may say that the 
trichosanthes colouring matter contains a substance which is not 
chlorophyll, but which on treatment with hydrochloric acid yields 
one of the constituents of phyllocyanin, which is itself probably a 
mixture of two substances. In chlorophyll a partial change is pro- 
duced by a very weak acid, so that extracts of certain leaves, such 
as those of the Virginian creeper, yield the modified spectrum, un- 
less care be taken to neutralise the acid before extracting the 
chlorophyll. It is possible that a somewhat similar change has 
been produced in the trichosanthes colouring matter by the tricho- 
santhin which occurs along with it in the pulp. 
* Jour. Chem. Soc., vol. xli. p. 334. + Annals of Botany, vol. iii. p. 86. 
