GALLS CAUSED BY GALL- WASPS 45 



cases, etc. That the species is injurious in many instances 

 there can be no doubt. It only frequents stub or young 

 oaks, not over 3 or 4 feet high. These, when they appear 

 in numbers in nurseries, they frightfully distort, and not 

 infrequently render saleless." 



The leaf -rolling saw-fly (Blennocampa pusilla) has of late 

 years attacked cultivated Roses in various parts of England, 

 in some cases to such an extent that no blossoms were 

 produced. 



Cultivated Orchids are sometimes attacked by Isosoma 

 orchidearum (see J. O. Westwood's paper in the " Gardener's 

 Chronicle," 1885, vol. xxiv., p. 84, on " Galls on the Roots 

 of Orchids"). The surface of the stem is covered with 

 distinct swellings, and exhibits necrosis in irregular patches. 

 There are circular or oval holes leading into cavities of 

 irregular form. The base of the leaf, and often the floral 

 sheath, is thickened and swollen ; other parts bear isolated 

 rounded swellings. Attacked buds are swollen, globular, 

 and thickened. Westwood observed these galls on a 

 species of Dendrehium, and Fitch found them on Cattelya 

 Triansei. 



