GALLS FOUND NEAR BOSTON. 69 



air. It was in 1877 that Dr. Adler published the results of his 

 experiments. 



I have myself endeavored to experiment on little trees of 

 Quercus alba, Quercus bicolor, and Quercus rubra, given me by 

 Mr. Dawson. I placed galls, whose flies were just ready to 

 escape, about the trees, and covered each tree with muslin, and 

 put them by an open window, where they could have fresh air, 

 and where I could watch them easily ; but the little flies sat 

 quietly upon the muslin, and did not appear to take the slightest 

 interest in the oak trees. Finally they all died or disappeared, 

 and no galls were ever produced upon the little trees. This may 

 have been because the leaf buds were not in exactly the right 

 condition, because they wanted blossom buds, or for some other 

 mysterious reason. 



Mr. Bassett says that where an oak tree or shrub abounds with 

 any given species, we may be sure that the other form also breeds 

 there, either on root, trunk, limb, or in bud, leaf, flower, or fruit, 

 and with this certainty established we ought to be able to find 

 them in ever}' case. 



These discoveries have a practical bearing. Should any galls 

 occur in such numbers as to be injurious to our oak trees, we can 

 fight them much better if we are acquainted with them in both 

 their forms than if we can only attack them in one. 



To those who wish to pursue the subject, Miss Clarke recom- 

 mended the account of Dr. Adler's discoveries from which she had 

 quoted. Its title is " Ueber die Generationswechsel der Elchen- 

 gal-Wespen." It appeared in the " Zeichschrift ftir wissenschaft- 

 liche Zoologie," Feb. 7, 1881. Also the article by Charles V. 

 Riley, in "Johnson's Encyclopaedia," on "Galls and Gall 

 Insects;" "Galls and their Architects," by Benjamin D. Walsh 

 in the "American Entomologist," Vols. 1 and 2, 1868, 1870, and 

 various other articles by Walsh, Riley, Osten-Sacken, Fitch, and 

 Bassett. 



The lecture was illustrated by specimens and photographs of 

 many varieties of galls, and the large audience paid most inter- 

 ested attention to all. At the close of the reading, a vote of 

 thanks to the essayist was unanimously passed. 



