THE BIRCH GALL-MITE. 9 



and states that he has " never failed to find the asci of an Exoas- 

 cus " on the leaves. , It would appear, therefore, that the 

 brooms on the Birch, at any rate in certain districts in Scotland, 

 are caused by a fungus. Dr. Buller says that he has often 

 examined the brooms on the Birches, in the Midlands, e.g. those 

 in Sutton Park, Lightwoods Park, and at King's Heath, but has 

 never succeeded in detecting any trace of an Exoascus on the 

 leaves. On the other hand, whenever he has examined the 





FIG. III. SILVER BIRCH AT KING'S HEATH WITH WITCHES BROOMS. 



buds with the aid of the microscope, he has always found this 

 particular mite. My own observations fully confirm Dr. Bullers, 

 and I think that there can be little doubt but that the-e are the 

 sole cause of the formation of the brooms in the Midlands. 



Figure II is taken from a photograph of one of three brooms 

 on a Silver Birch in the garden of J. B. Finnemore, Esq., 

 Edgbaston. For the photograph of Figure III I am indebted to 

 the kindness of my colleague Dr. Buller. 



