862 THE AMERICAN NATURALIST. [Vor. XXXIX. 
In his Origen of Floral Structures, Henslow has drawn an 
analogy between the gall and the flower. He intimates that 
the gall is the result of the shortening of the axis due to punc- 
turing in the depositing of eggs by insects, and thus represents 
a lessened growth of twig. I believe that the gall does not 
represent a shortening of the axis, but, on the other hand, rep- 
resents a special growth of scales in addition to the normal 
growth of twig. I base my belief on the following observa- 
tions : — 
1. The scales of the gall have not the normal leaf arrange- 
ment or venation. From a single clump of willows (S. bebbiana) 
I gathered a number of twigs and galls. The lateral buds of 
this willow have the two fifths arrangement. If the gall repre- 
sents a shortening of the axis the scales ought to show some 
such arrangement, allowing for a reasonable amount of displace- 
ment owing to crowding. While the general arrangement of the 
scales was in whorls, some showed a spiral arrangement but 
never thetwo fifths. I examined in detail about a dozen galls to 
determine this. Moreover the scales do not very much resemble 
the leaves of the willows. They differ in shape and margin and 
show little or no venation and never the venation of the leaf. 
2. The gall-bearing shoot is oftenest longer than the non- 
gall-bearing and develops more lateral buds. From this same 
bunch of twigs I took 28 bearing the crooked galls and the 
same number of non-gall-bearing twigs. The average number 
of lateral buds to the gall-bearing twigs was 20, while the aver- 
age to the non-gall-bearing twigs was only 161. Eleven gall- 
bearing and ten non-gall-bearing twigs were taken from the 
same part of the plant, having had, as nearly as could be deter- 
mined, the same conditions of growth. The former had an 
average of 174* lateral buds and an average length, from origin 
of the twig to the base of the gall, of 6.84 inches, and the latter 
had an average of 17 lateral buds and an average length to base 
of terminal bud of 6.825 inches. In every case the twigs were 
of 1904 growth. General observations of various clumps of wil- 
lows confirmed the foregoing results. However, in one case the 
average length of five pubescent gall twigs (Salix cordata) was 
1.13 inches less than the average length of seven non-gall-bear- 
