ii6 The Ohio Naturalist. [Vol. IV, No. 6, 



all parts of the gall at the same time, but gradually moves out- 

 ward over the surface of the leaf, thus increasing the size of the 

 gall and drawing its food supply from the newer part thus formed. 

 When the attack is made upon the flower we have a mass of 

 distorted tissue which is structurally the same as that produced 

 in the leaf gall (Figures 72a, b). The floral envelopes are the 

 first to suffer from the attack, the ovar}' with its contents is the 

 next greatest sufferer, while the stamens are frequently unaffected. 

 It is evident that the attack upon the flower must be made very 

 early in order to cause complete destruction. Very frequently 

 the floral envelopes will be very much deformed and the ovary 

 and the stamens ver}^ slightly affected. In other cases the ovary 

 will be very much enlarged and its chambers practically obliter- 

 ated. It is evident that the attack upon the ovary must be made 

 very early to produce a great deformity. The partial immunitj' 

 of the stamens is probably due to their being very nearly mature 

 before the opening of the bud. 



2. GAI^LS OF CECIDOMYIA. 



Cecidomyia anthophila O. S. — on Solidago canadense L. (Figs. 

 73a, b), makes the attack early and completely prevents the open- 

 ing of the bud. The gall is in the form of a hollow cone. The 

 transformation is so complete that the location is the onl}- evidence 

 that the gall is produced from a flower bud. A section of the 

 gall shows the nutrient layers of the cells next to the larval 

 chambers, large parench^^ma cells near the outer epidermis, and a 

 number of rather weak fibro- vascular bundles. 



Cecidomyia sp. — on Ratibida pinnata Barnhart (Figs. 74a, b, c). 

 The entire bud is transformed into a gall with the larva in a 

 chamber in what was originally the ovary. All the floral parts 

 have become modified and united to form the gall. A section of 

 the gall (Fig. 74c) shows that the cells are more uniform in size 

 than in the preceding galls and that the fibro-vascular bundles 

 are practically obliterated. 



Cecidomyia sp. — on Prunus virginiana ly. (Figs. 75a, b). My 

 specimens of this gall were mature. I am unable to say at what 

 time the gall originates, but it reaches its maturity with the fruit. 

 The gall is somewhat larger than the fruit, but otherwise resem- 

 bles it closely. The larva makes its exit through an opening at 

 one side of the stem. The larval chamber is very large, thus 

 giving the gall a l^ladder-like character. The cuticle is well 

 developed and the parenchyma cells below it are ver}' large, while 

 the cells next to the larval chamber are much smaller. Weak 

 flbro-va.scular bundles are ahso present. The wall of the gall 

 (Fig. 75b) is much thicker than the wall of the fruit at this time 

 (Fig. 75a), and parenchyma cells are much larger. The charac- 

 teristic stone (sclerenchyma) of the fruit is never developed in 

 the gall. 



