AMERICAN 
AUG 1 1 1916 \\ 
JOURNAL OF BOTANY 
Vol. Ill 
July, 1916 
No. 7 
THE DEVELOPMENT OF THE PHYLLOXERA VASTATRIX 
LEAF GALL 
Harry R. Rosen 
L Introduction 
Phylloxera vastatrix Planchon [Stebbins (27) uses the synonym 
Phylloxera vitifoliae Fitch] is the plant louse which was introduced 
into Europe from America and became one of the most dreaded ene- 
mies of the European grape vine. On American vines the insect 
usually attacks the leaf producing ugly cecidial growths but not 
seriously impairing the health of the plants attacked. On European 
vines, however, the insect does most of its work on the roots, be- 
coming a very destructive pest. Much has been written concerning 
the life history of this parasite, a large part of which has been brought 
together by Viala (29). 
11. Occurrence and Appearance of the Mature Gall 
The material for this paper was gathered in the vicinity of Madison, 
Wis. The profuse growth of the wild vines of Vitis vtdpina L., to- 
gether with the ease with which one can 
find the Phylloxera galls, made this gall a 
desirable one to study in this region. My 
observations extended over a period of two 
growing seasons, during which time I have 
been able to observe hundreds of these 
cecidia. Although Cook (6 and 7) and 
Stebbins (27) found the galls on both the 
upper and lower surfaces of the leaves, I 
have found them only on the lower surface. 
Houard (15) and Cornu (8) mention only 
the lower surface as the bearer for the 
[The Journal for June (3: 261-336) was issued July 15, 1916.] 
337 
Fig. I. A gall as seen on 
the lower surface of the leaf 
through a hand lens. Mag- 
nified about 3 times. 
