The Ohio Naturalist. 
[Vol. IV, No. 6, 
1 16 
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 structural!}’ 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 frequentl}’ unaffected. 
It is evident that the attack upon the flower must be made very 
earh’ in order to cause complete destruction. \’ery 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 ver}’ much enlarged and its chambers practically obliter- 
ated. It is evident that the attack upon the ovary must be made 
ver}’ earl}’ to produce a great deformity. The partial immunity 
of the stamens is probably due to their being very nearly mature 
before the opening of the bud. 
2. GALLS 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 only 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 parenchyma 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 ovar}’. 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 tlie preceding galls and that the fibro-vascular bundles 
are practically obliterated. 
Cecidomyia sp. — on Prunus virginiana h. (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 otherwi.se 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 bladder-like character. The cuticle is well 
developed and the parenchyma cells below it are very large, while 
the cells next to the larval chamber are much smaller. Weak 
fibro-vascular bundles are also jre.sent. 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. 
