ii8 
The Ohio A'aturalist. 
[Vol. IV, No. G, 
ripes (Figs. lo, 43), and P. acericola (Figs, ii, 45). Tliese con- 
volutions result in the formation of a more or le.ss well defined 
cavity, and trichomes are developed in great abundance in the 
younger stages ; (3) Thickening of the parts which become cov- 
ered with an abundant growth of trichomes as in the case of E. 
anomalum (Figs. 47, 48). 
The Phj’toptus galls show two fairly well-defined zones, the 
outer made up of rather large cells and the inner of much smaller 
cells, which are ver}’ rich in protoplasm and which supply nour- 
ishment for the young animal (Fig. 77). As the galls approach 
maturity the protoplasm disappears, first from the outermost cells 
and lastly from the cells on the inner surface. As the protoplasm 
di.sappears the tannin accumulates in great abundance (Fig. 78). 
2. GAI.LS OF THE APHIDID.A.E. 
Mail}' of the Aphididae galls produce trichomes which soon 
disappear. At first all the cells contain protoplasm and divide 
rapidly, but as the galls approach maturity the tannin increases 
in abundance. 
Schizoneura americana Rilej’ ( Fig. 12), Colopha ulmicola F'itch 
(Fig. 13), and Hormaphis hamamelis Fitch ( F'ig. 15) have been 
considered in Part I. 
In Pemphigus populi-transversus (Figs. 55, 56) and P. p.-caulis 
(P'igs. 57, 58) the thickness of the walls of the galls is much 
greater than an}- other members of this family and the cells are 
more uniform in character. These galls are especially well .sup- 
plied with fibro-vasular bundles and are very dense. 
In P. vagabundtis (Fig. 112) we have a gall in which main- of 
the cells are elongated similar to C. ulmicola and H. hamameli.'-. 
Its clo.se structural resemblance to C. ulmicola and H. hamamelis 
and unlikeness to P. p,-tran.sversus and P. p.-caulis is due to the 
fact that P. vagabundus, C. ulmicola, and H. hamamelis are 
formed on the blades of the leaves, while P. p.-transversus and 
P. p.-caulis are formed on the petioles which are made up largely 
of fibro-va.scular tis.sue. My specimens of these galls were mature, 
and I am therefore unable to .say an3-thing concerning their early 
stages. 
In the Pli3-lloxera galls all tie cells are at first rich in pro- 
toplasm and the tannin does not form in abundance until ver}' 
late. The two zones are fairh- prominent. In P. c.-caulus Phtch 
on H. ovata, a gall which forms on both blade and petiole of the 
leaf and akso on 3-oung stems large intercellular .spaces are formed 
near the surface. 
3. G.\ELS OF P.SYI.UDAE. 
Pachypsylla c. -mamma Riley has been described in Part V 
(Figs. 59, 60). 
