SECTIONAL TRANSACTIONS.—K. AAS 
in fatty contents, later become dark coloured and then black, and obviously 
degenerate. Normal production of reproductive bodies is invariably preceded 
by the appearance of a pink pigment in the mycelium, and no pink pigment 
appears in darkness. The dependence of the hyphe on light, both for the 
production of this pink pigment and also for the development of the reproduc- 
tive bodies, suggests that possibly the two phenomena are causally connected. 
4. Miss C. A. Prarr.—The Staling of Fungal Cultures. 
The problem is considered from the point of view of the change brought 
about in a liquid medium (Richards’ solution) by the growth in it of a fungus 
(Yusarium sp.). ‘Staleness’ of the medium is not due to exhaustion of food. 
The medium becomes alkaline, i.e. its pH value changes from 4.6 to about 8.6. 
This is mainly due to the accumulation of potassium bicarbonate. Now, in a 
medium of pH=8.2 produced by potassium bicarbonate, growth is inhibited; 
potassium carbonate and potash have no sensible effect at this pH. Nevertheless, 
acidifying only partially restores the germinative capacity of the stale medium. 
Acidification liberates simple organic acids, metabolic products of the fungus. 
These acids are growth inhibitors, hence the poor growth in an acidified stale 
medium. The salts of organic acids are not toxic, i.e. are not active in the 
alkaline medium. 
The ‘staleness’ of the medium, i.e. its loss of germinative capacity, is 
therefore ascribed to the accumulation of potassium bicarbonate due to carbon 
dioxide from respiration. 
5. Prof. F. E. Luovp.—The Fluorescent Pigments of the Cyano- 
phycee. 
It has previously been shown that the fluorescence of the blue-green alge 
is microscopically observable in living material, that of the species containing 
phycocyanin as deep red, that, of those containing phyccerythrin as orange, 
corresponding to our previous knowledge of the pigments involved. A third 
condition is here reported represented by a species of Arthrospira previously 
thought to be non-fluorescent (Science, I1., 59, 241), but which is now found 
paralleled in pigment content by Oscillatoria chlorina. These two forms are 
both yellow-green by transmitted light and blue by reflected light (dark field 
condenser with inverted light cone). The Oscillatoria is blue-fluorescent in 
ultra-violet (fluorescence microscope). It is expected that a yellow, blue- 
fluorescent pigment will be found, and, if so, may be named phycoxanthin. The 
emplacement of these pigments will be discussed. (Illustrated by colour-procesg 
lantern slides.) 
6. Prof. W. T. Gorvon. 
Genus Pitys. 
Report of Committee of Section C (Geology) to investigate the fossil flora 
of the Lower Carboniferous rocks as shown at Gullane, Haddingtonshire (Kast 
Lothian). 
The Structure and Affinities of the Genus Pitys.—One ideal which the 
palzontologist keeps before him in describing fossil remains is to present to 
the mind a picture of the particular organism as a living, working machine. 
Such an ideal is, however, rarely realised. The fortunate discovery of some 
well-petrified plant-remains in a volcanic ash at Gallane has allowed this ideal to 
be realised to a large extent in the case of the genus Pitys. 
It may not be without interest to recall to mind that the first fossil plants 
described from thin sections belonged to that genus, and that the types then 
recorded (Witham 1831) had attained the size of forest trees. At Gullane, in 
addition to fragments of such large trees, we have now to record the discovery 
of twigs, ciothed with bark, and, in two instances, buds with their leaves 
attached. The results of the investigation were presented in a paper to the 
Royal Society of Edinburgh in June of last year. 
_ While the discovery of the cortical tissues completes our knowledge of the 
general anatomy of the stem of Pitys, greater interest centres round the leaf 
structures. These undoubtedly indicate that the leaves were really only petioles, 
The Structure and Relationships of the 
