536 BOTANICAL GAZETTE [JUNE 
catalogue of the zoocecidia of Europe and the basin of the Mediter- 
ranean, a work which in 1908 (supplement 1913) was expanded by 
Hovarp (6) into the largest systematic cecidological work in exist- 
ence. This final general European work comprises the description 
of 1950 zoocecidia. 
Basis and plan of work 
The data from which the following summary is drawn were 
obtained during a period of 4 years, in which field studies in Con- 
necticut, Ohio, and Kansas were supplemented by a thorough 
canvass of the highly scattered cecidological literature. 
It may be of interest to mention the simple and, it is believed, 
practical scheme which has been followed in the arrangement of the - 
792 types described. The plant genus was made the unit under 
which the galls were grouped. This is in contrast to HOUARD’S 
plan; he used the species, a plan which necessitated a vast amount 
of repetition, since innumerable galls occur on more than one species 
within the genus. It is a striking fact that very few galls are found 
upon more than one genus. In the study of the galls of the north- 
eastern United States, data concerning the plant species bearing 
the gall have been included with the descriptive material. To 
assist in locating the descriptions, keys were worked out for the 
genera having more than 6 or 8 species. A brief bibliography 
presenting the most important references was appended to each 
description. 
The plant genera in the work have been arranged alphabetically. 
The galls under each genus have been aggregated according to the 
classification of the cecidozoons. It is thus evident that artificial 
classification has been pursued throughout. At the present time 
any classification of zoocecidia must be artificial. The morpholog- 
ical data available, particularly of an anatomical nature, are far 
too meager to make possible anything approaching a natural 
classification. 
Summary of numerical data 
In the case of all of the following figures presented, it acai be 
understood that they are but approximations. So new is the field 
of systematic zoocecidology in America, and so incomplete and 
