68 MASSACHUSETTS HORTICULTURAL SOCIETY. 



form of conical blotches, projecting from both surfaces of the leaf, 

 but are more prominent on the upper surface, and are about one- 

 fourth of an inch in diameter. Each gall produces three or four 

 small gall-flies which emerge about the first of July, and soon 

 disappear ; where they went to, nobody knew or seemed to know, 

 till I found out their secret last spring. Before the leaves 

 appeared, I visited a thicket of young oaks, where I had found 

 these galls very abundant in past years, hoping to find their 

 progenitor, whoever she might be, ovipositing in the buds of these 

 oaks, — but I was too early ; she had not begun her work. But 

 where was she napping at the time? The question was not by 

 any means a new one to me. The soft, sandy loam at the roots 

 of a clump of oak bushes yielded to my fingers, and I soon had 

 one of the main roots laid bare. Judge of the joyful surprise it 

 gave me to find the bark of this root a solid mass of blister-like 

 swellings." 



In these swellings Mr. Bassett found minute larvae, and others 

 evidently a year older than the first ones, but not old enough to 

 produce the gall-flies, and yet on putting the roots in sand under 

 glass, in a few days he reared perfect gall-flies, identical with 

 those he saw ovipositing on the low, white oak bushes, and, mark- 

 ing the trees and twigs, he found that when the leaves were fully 

 grown, they bore futilis galls in abundance, but no other species. 

 So the connection between the root galls and the futilis leaf galls 

 was proved. 



Mr. Bassett's discoveries are the result of observations made 

 in the field, but those of Dr. Adler were from experiments on 

 young oak trees grown in pots. Each pot bore its number, and 

 each pot served for the researches on a single species. After 

 gall-flies had been brought to the trees, they were guarded until 

 they began to sting the buds ; in order that they should not 

 escape, or another gall-fly lay on the same tree, a cover was 

 placed over them ; at first Dr. Adler used glass receptacles, but 

 he was incommoded by the moisture which gathered on the glass, 

 and hindered observation of the gall-fly, and then he used covers 

 that were partly glass and partly gauze. The four to six year old 

 trees suited him best, and only those which had well-developed 

 buds were available. But of course these little oaks cannot serve 

 for experiments on species which only la}- their eggs in blossom 

 buds ; these must be observed with all possible care in the open 



