8 BRITISH OAK GALLS. 
portant pigment, and with it are associated lipochrome 
pigments, whose nature and amount determine the 
exact shade of green displayed by the vegetable 
organs. 
“The fixed or lipochrome pigments occur in the 
form of solid particles in the cell, and the free or 
anthocyan pigments, in solution in the cell sap” (loc. 
cit., p. 70). 
Galls, which during their median or final stages of 
growth are yellow or orange, obtain their tints from 
the lipochromes, which take the place of the 
chlorophyll-green. 
A series of pigments known as anthocyans, i in a 
soluble condition, are blended with the cell-sap; they 
form the colouring materials and manifest themselves 
most prominently in the epidermis and underlying 
tissue. 
Anthoxanthin is the yellow pigment; it is common 
and widely distributed. In the case of galls it appears 
to manifest itself as soon as the chlorophyll-green 
diminishes, and becomes intensified until the orange is 
reached. Red is the most prevalent, and all the tints 
are due to lipochromes or to anthocyans. Much of it 
can be dissolved out in water. 
It may be remarked that red is more common in 
galls maturing in late summer and in the autumn than 
those of spring time—a feature paralleled in the 
autumnal tints of fohage and fruits. 
Dr. Newbigin is of opinion that, in plants, tannin 
plays the part of a brown pigment. This is more than 
probable in oak galls since very few of those which 
develop in the spring and mature in early summer 
change to brown, whereas almost all the autumn forms 
assume that colour at a comparatively early age. 
The formation of tannin and its oxidation are most 
active during the time these galls are growing. 
