270
THE ESSEX FIELD CLUB.
water Alga, Cladophora aegagrephila, and made some remarks upon this interest-
ing plant, which are embodied in the note in the Essex Naturalist (ante,
pp. 180-1).
Thanks were voted to Mr. Scourfield and Mr. Holmes for their communica-
tion.
Change of Colour of Fucus by heat.—Mr. W. Cole demonstrated the
very rapid change of colour of the thallus of the sea-weed, Fucus vesiculosus,
when placed in hot water. The deep brownish-yellow colour of the alga was
changed with startling quickness to a vivid green. Mr. Cole said that the
commonly accepted explanation of the brown colour of such sea-weeds was that
the green chlorophyll was covered up and masked by a brown colouring matter
(phycophaein) and a yellow one (phycoxanthine) and that fresh-water dissolved
out these colouring matters and so exposed the green chlorophyll. This
experiment was usually made by means of cold fresh-water, and the supposed
solution of the brown or yellow colouring matters took some days to accomplish.
The sudden change of colour in hot-water was new to the exhibitor, but
probably was known to botanists. Mr. Cole explained the usual hypothesis
found in botanical books of this masking of the chlorophyll in deep-sea water.
Some remarks on this subject were made by Mr. Dymond and Prof, Meldola,
who suggested some chemical change in the pigment rather than the solution of
a brown colouring-matter.
Prof. Boulger said that he had been long familiar with the solution of the
brown colouring-matter of Fucus revealing the green chlorophyll. The use of the
Fucus in the so-called "iodine bath'' was alluded to. Many people when they saw
the boiling water, poured on the alga, become thickly discoloured with brown
were under the delusion this was all iodine. As a laboratory experiment it was
useful as showing the student that all algae, even those not obviously green,
contain chlorophyll, and that it differs in solubility from the other colouring-
matters by which it may be masked.
[Since this exhibit Mr. Whitehead and I have made a few experiments, and'
we have found that we could bring about the change in colour by simply
warming the nearly dry Fucus—there could be no solution of the brown
matter in this case. The change could also be induced by placing the plant in
chloroform vapour. In the last edition of Strasburger's Botany the problem is
thus alluded to :—" Recently Hans Molische has attempted to prove that the
brown colouration of the Diatoms, the brown Alga", and especially of a sapro-
phytic Orchid (Neottia nidus-avis) is not due to a mixture of a brown pigment
with chlorophyll. He regards it as due on the one hand to a single pigment,-
phaeophyll, which is nearly related to chlorophyll and readily undergoes a
chemical change into ordinary chlorophyll."—W. Cole.]
The President made some announcements of future fixtures, and the meeting
closed, the company walking to Theydon Bois station to take train homewards.
THE 28th ANNUAL MEETING AND 264th ORDINARY
MEETING.
Saturday, May 23RD, 1908.
The Annual Meeting was held at six o'clock in the room at the Technical
Institute, Mr. Miller Christy, President, in the chair.