538 BOTANICAL GAZETTE [JUNE 
DISTRIBUTION BY PLANT FAMILIES—Continued 
iy pericacene ace 12 SECA COAG os eck ry Labiatac. so.  o 14 
Wiglacene 5 i as 2: Prinmulacesei 34.65. 1. Solanaceae. 2.0.2 2. 3 
RMCCACERE. Ve eect t RDONRCEEE.. 6 cess 2 Scrophulariaceae..... 2 
Lyiwacese. sii c ess; e AMPRCONE. os. ode 354 6 Bignoniaceae......... I 
Onagracese : 04.06.4535 x Apocynacene.i 6.6.65 %- Rubiaceae. cis (sce 3 
Araliacest &, . 0 isc. 1 Asclepiadaceae....... 2 Caprifoliaceae......... 16 
Unobelliferae... 3.0.5 t Convolvulaceae...... 1 -Compositee: 5.0.8. <3 121 
CORMACORE 625 asi TT Verbenaceae «o. 6 5 6s ss 
The striking fact brought out by this list is the extreme irregu- 
larity of the distribution. Many of the larger families have few or 
no galls, while on the other hand a few of the smaller families, 
particularly the Fagaceae, possess many cecidia. Quercus alone 
has 176 galls, of which 157 are cynipid types. FELT presents 277 
as the approximate figure for the cynipid galls on the American 
oaks. The Cynipidae-Quercus situation in Europe as well as in 
America presents the most striking example of gall evolution within 
a single genus of plants related to a comparatively few (9 or 10) 
closely related genera of insects. 
It is worthy of note that such large families as the Caryophyl- 
laceae, Cruciferae, and Boraginaceae contain no gall-bearing species. 
The Umbelliferae possess but a single gall. The widely distributed 
tree species Platanus occidentalis does not bear any zoocecidia. 
The problem in distribution on the plants presented by the 
preceding list is an exceedingly difficult one and probably cannot 
be answered on the basis of the physiological information at present 
available. This intimate and constant relation between specific 
insects and specific plants forms one of the most significant phenom- 
ena in the field of cecidology. 
As far as data were obtainable, figures were worked out indi- 
cating the distribution of the galls on the plant parts, with the 
following result: 
DISTRIBUTION ON PLANT PARTS 
On leaf blade (of these 52 are “blis- CO BOB og eis che ele eet 12 
ter OOS) ia aay SR GOW cs ce te eee 27 
On petiole (most of these occur also From buds forming a rosette type... 47 
OR MAGE) i 47. From buds forming a solid concentric 
On stem (8 per cent of these occur type 
aloo on the leat). os, cc 208 
Ce Wee Rk ee ae ee ee ee a ee 
