GALL MITES. 363 



CASE onlv on leaves such as those of Cydonia and Sorbus, which have 



XVII. ' 



a very felt-Hke underside, have they been found on the upper. 

 The old botanists described these lea. pustules also under the 

 name of Erineum (E. pyrinum, Pers., and E. torminalis, Fee). 



On the Thorn. 

 Erineum oxyacanth^, Am. 

 Every here and there the edge of the leaf is turned up; under- 

 neath it is of a greenish yellow colour. These turned up parts 

 are full of Erineum rust, in which lives a transparent whitish, 

 conical cylindrical mite, | of a millimetre in length. The mites 

 appear in May. Besides the thickened edges, they form light- 

 brown egg-shaped bells, and club-like galls. 



On the Plum. 

 Cecydoptes pruni, Am. 

 This, according to Dr. L. Kirchner, produces galls on the young 

 twigs of the plum tree. Dr. Amerling discovered them at Prague, 

 and although they usually only appear on trees that are growing 

 old, and whose death is approaching, Dr. Kirchner has besides 

 noticed them on young and healthy plants, whose death they 

 cause. 



On the Vine. 

 Phyllerium vitis, Fr. 



This was well known to the earlier botanists. It consists of 

 warty simple or divided transparent spots, scattered over the under 

 side of the leaves of the vine. It may very possibly have in some 

 instances been confounded with the work of Phylloxera vastatrix. 

 The mites that produce it are so small that they can only be seen 

 by means of a strong magnifying glass. They are fully described 

 by Von Landois, to whose papers we have already referred. 



A peculiarity in regard to the appearance of this Phyllerium 

 was noticed every year in succession in the botanical garden at 



