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. 

 (■it., p. 70). 



Galls, which during their median or final stages of 

 growth are yellow or orange, ol)tain their tints from 

 the lipochromes, which take the place of the 

 chlorophyll-green. 



A series of pigments known as anthocyans, in a 

 solul)le 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. Eed 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 foliage and fruits. 



Dr. Newbigin is of opinion that, in plants, tannin 

 plays the part of a brown pigment. This is more than 

 ])rol3able 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. 



