16 Transactions of the eee 
simply causes a more rapid solution to be obtained by its affinity 
for the colouring matter in the still living alge, or by starting the 
decomposition of the Oscillaria favours the solution of this part of 
its pigment. Any such action of albumen would be very different 
from Mr. Sheppard’s monad-mystery. 
It is worth noting that Cohn speaks of a red modification of 
his Phycocyan (which is usually blue in solution with carmine 
fluorescence), not to be confounded with his Phycoerythrin, which 
gives an exact parallel to Mr. Sorby’s observation of a blue and a 
red condition of the fluid from such confervoid growths as Mr. 
Sheppard’s. 
The discussion about the origin of this colour is really almost 
ludicrous, and very nearly as devoid of justification as would be a 
discussion as to the origin of the yellow colour when saffron is put 
into water. The drawings of Mr. Sheppard’s conferyoid growth 
which you were so kind as to send for my inspection, prove it to 
be one of the true Oscillarie as defined by Kutzing. Some of a 
growth which Mr. Sorby has had the great kindness to send me 
from Derbyshire belongs to the same species. Now it is an esta- 
blished fact that these alge, as well as certain lichens and fungi, 
give colouring matters soluble in water after the death of the plant, 
and often fluorescent. It is a serious obstacle to the progress of 
knowledge when the work of previous observers is ignored, and 
wild speculation is used instead of the comparison of fact with fact. 
The paper of Cohn in Max Schultze’s ‘ Archiv,’ 1867, Part I., must 
be looked at by those who wish to discuss this question ; also that 
of Dr. Askenasy in the ‘ Botanische Zeitung,’ July 1867, which is 
a most interesting memoir, giving intensity diagrams of the spectra 
of—1, a colour from Oscillariz, allied to or perhaps the same as Mr. 
Sheppard’s, and as Cohn’s Phycocyan, though there is discrepancy 
in the figures given by the three authors of the spectrum, which is 
easily accounted for; 2, of a similar colour from the lichen Pelti- 
gera canina; 3, of another similar colour from Collema. The 
colouring matter known as Cudbear, obtained from a lichen, may 
be also studied in comparison with the colour from Oscillarie. 
It is a mistake to suppose that the mats of Oscillarian growth 
are dead because they have such a powerful and unpleasant smell. 
It is not until they are dead that the cells of the plant allow the 
colouring matter to pass into the water, but it is easily to be recog- 
nized in the living fronds. Its presence in the water is the result 
of the decay of the algze, but it is formed in the living plant. 
I am able to give a very complete answer to the theories as to 
the formation of the colour outside the plant and after its death 
‘(which are, indeed, inconsistent with all analogy) by the study of 
some of the growth—identical with Mr. Sheppard’s—for which I 
am indebted to Mr. Sorby’s kindness. The two bands described 
