Kinsey: Gall Wasp Genus Cynips 
115 
dermis, and now migrates by way of the canal into the de- 
veloping gall. The empty egg is left in its original location 
in the xylem, the cavity in which it lies is gradually filled with 
a scar tissue (the development of which may be the means 
of forcing the larva to migrate thru the canal), the canal 
itself is closed at its base by the newly developing tissue, and 
the insect is thus enclosed in a larval cell in the heart of the 
gall. 
Once having broken the leaf epidermis, the galls of folii re- 
main attached to the leaf only by a very slender pedicel which, 
however, may contain a score of vascular bundles. The cytol- 
ogy of the mature gall has been described by Beyerinck 
(1883), by Hieronymus (1890), Fockeu (1889), and Weidel 
(1911), and its four zones of tissues are evident with a low 
power lens. These layers are: (1) An epidermis with few 
stomata, altho there are some stomata (contrary to the state- 
ments of some writers) on the basal two-thirds of the galls; 
(2) a parenchyma which has numerous, intercellular air 
spaces toward the outside and a much-branched, air-filled, and 
in the older gall a spongy parenchyma toward the center of 
the gall; ( 3 ) a protective zone of compacted tissue which, 
however, is not so well developed as it is in N enrol erus ; and 
(4) a nutritive zone which is well developed, being formed 
of rounded cells that contain a granular protoplasm and drop- 
lets of oil. The nutritive zone lines the inside of the larval 
chamber and is absorbed, as with other Cynipidae, by the 
larval folii without the development of waste of any sort that 
can be detected within the larval cell. The collenchyma, 
which lies between the epidermal and parenchymal layers in 
most galls of Cynips, is absent in folii. 
The mature galls of folii may weigh (acc. Trotter 1909) as 
much as 4.84 g. and average (acc. Kieffer 1901) between 2,0 
and 3.0 g. This may be as much as twice the weight of the 
leaf which bears the gall, and Kieffer found that one leaf 
which bore 16 galls was burdened with 18 times its own 
weight. Most of the weight of these fresh galls is, of course, 
due to the water they contain, but because of the scarcity of 
stomata on the epidermis of the galls, they dry out very 
slowly. Trotter (1909) gives the following data on this point: 
A fresh leaf weighing 0.70 g. dries in 9 days to 0.30 g. 
A fresh gall weighing 4.84 g. requires 120 days to dry to 
0.60 g. 
