THE OAK. 21 



The galls of commerce, I may here remark, are similar 

 ill their nature to those already mentioned. They are 

 produced by a dwarf species of Oak (Quercus infectoria), 

 which rarely attains the height of six feet, growing in Asia 

 Minor and Persia. The insect which occasions this gall is 

 of a pale colour, and may be often found in the galls sold 



4'^ 



>i 



in the sliops of druggists. The latter vary greatly in the 

 (Qualities on account of which they are employed; those 

 which still contain the insect, and are known by the name 

 of black, blue, or green galls, being the best : while those 

 from which the insect has escaped, which are called white 

 gaUs, do not contain more than two-thirds of the astrino-ent 

 qualities of the former. They are used for making ink, 

 for dyeiug, and for medicinal purposes. 



About the year 1840 a gaU appeared in the southern 

 and western counties which has since spread itself over the 

 whole of England. This is not only more conspicuous 

 than any other native kind, but threatens to produce 

 seriously injurious effects. This species is spherical in 

 shape, perfectly smooth, and about one inch in diameter. 

 It is seen in the greatest abundance on the annual twigs 

 of young trees, which sometimes have as many as a dozen 

 .or more in close proximity. These galls act injuriously, 



