No. 468.] THE WILLOW CONE GALL. 861 
_ The three cone galls on which I have based most of my study 
are all found in the vicinity of Lake Forest, Illinois. I also 
gathered some material in southwestern Wisconsin. They are 
formed from apical buds. In structure and appearance they are 
much alike but they have some characteristic differences. The 
three are; — 
I. A pubescent gall found growing on Salix cordata Muhl., 
which corresponds in every particular to the gall found by Walsh 
on the same willow. This is the gall .SaZrezs strobiloides O. S. 
(Fig. 1, e and f). It is usually somewhat spherical but occa- 
sional galls have the central scales prolonged into a loose tip. 
It is the dense silvery pubescence which distinguishes this gall 
most clearly from the others. 
2. A cone gall usually more tapering than the above and 
lacking the dense pubescence. Its marked characteristic is a 
decided curve or bend in the twig just beneath the gall (Fig. r, 
a, b,c). In every respect the gall corresponds to .SaZzzs gna- 
phaloides Walsh, but in no case have I found it on Salix humilis, 
the willow to which Walsh accredits it. Instead, I have found 
it in great abundance on Salir bebbiana. 
3. A gall corresponding exactly to .SaZezs gnaphaloides, 
except that the twig is straight (Fig. 1, 7), was also found on 
Salix bebbiana, the Salix rostrata of Walsh’s paper. These 
galls were not in such great abundance and were usually to be 
found on the same plant with the gall S. gunaphaloides. In some 
two or three cases small shrubs bearing only a few galls had all 
straight-stemmed ones. On one shrub with 37 galls, 9 were 
straight and 28 were crooked. From another clump of willows 
(S. bebbiana) I gathered 65 galls, of which 57 were crooked and 
only 8 straight. In both cases there was a gradation in the 
matter of the crook. 
Since I shall show a little farther on that these three galls 
have the same maker, it is evident that the distinction between 
the first and the others may be due to the peculiar reactions of 
the different willows to the stimulus which causes the growth 
But in the case of the two galls on S. bedbiana the 
of the gall. 
It will be neces- 
cause of the difference does not seem so clear. 
sary to observe the beginning of the gall to see if this can be 
determined. 
