Marcu, 1915-] THE ORCHID REVIEW. gt! 
mises THE CHEMISTRY OF FLOWER COLOUR. ears) 
A the meeting of the R.H.S. Scientifie Committee, held on February 
and, an interesting account of the chemistry of flower colour was 
given by Dr. Frederick Keeble, F.R.S. The formation of colour in flowers 
is one of the physiological problems of plant life that has remained some- 
what in the background, owing to the difficulties encountered in 
investigating the minute quantities that often suffice to form an intense 
pigment, and the factors that may completely change the colour of the 
whole flower or of any particular section. Colour production is a bye- 
product of the great process of life. The different colours are due to the 
varying colour of the cell sap, to the different distribution of such cells in 
the tissues, and also to the various combinations of dissolved colouring” 
matter with the yellow, orange, red, and green chromoplasts. 
It was demonstrated by a series of experiments that an extremely close 
relationship exists between the .anthocyan pigments: of the flower, blue, red, 
‘magenta, and pink, and oxydases, which lends sypport to the view that: 
they are due to the action of oxydase on chromogens. The latter are 
colourless bodies which are liberated from the living substance of the plant, 
and unite with oxygen to form various pigments. The rate and extent of 
the oxydisation are important factors, this depending upon the constitution 
of the cells situated at different parts of the flower. Delay in development 
‘may also occur in young or starved plants, possibly due to the lack of 
chromogen and the oxydising agent. Richly coloured flowers generally 
occur on vigorous plants. 
In many flowers a beautiful system of darker veining may be observed 
and until recently these veins were regarded as the means by which the 
colour was brought up from the plant and diffused over the flower. Dr. 
Keeble, however, suggested that these veins pour out some material 
necessary for the process of coloration, without which the chromogen, or 
mother of pigment, is unable to develop. Many flowers have white patches 
where both chromogen and the oxydising agent are present, but where” 
the presence of a third substance exerts an inhibiting or paralysing effect on 
the process of coloration. Albinism may result from lack of chromogen, or 
from the presence of a paralysing factor, which prevents the development 
_of colour. 
- At the conclusion of the lecture specimens of the anthocyan'pigments, as- 
prepared by Willstaétter and Everest, were exhibited. 
At the meeting of the Orchid Committee held on February 16th Mr. J- 
Charlesworth exhibited a series of ten forms of Odontioda Brunette (Oda- 
