1918] WELLS—ZOOCECIDIA 541 
In addition to the above two tables KtisTer has, in his classifica- 
tion of cecidia, furnished the basis for another table in his analysis 
of the prosoplasmas. These he divides into four groups: the leaf 
edge “roll” galls; the diverticulum or outpouching types; the 
“walled”? (umwallungen) forms, whose walls grow up about the 
superficial larva; and the concentric (mark) cecidia whose larvae 
inaugurate gall formation from a point within the tissue. In the 
following list this classification was extended to include so far as 
possible the kataplasmas also, since a great many of these latter 
galls can properly be placed under some one of the preceding four 
groups. The 58 “rosette” and the 28 erineum types cannot be 
included. 
NUMBERS OF VARIOUS GALL TYPES 
Leat edge “roll” types: 2.26. 5c: 32 Concentric types 
Diveetiralim tuna a eR ee ee ak 145 
saree dace CON GEREN SS aes Vl ves ba 184 
— or leaflet fold along mid- el ctr Hath. os cs 5s 36 
pence 1 Pa ne eee eee pre ee in the above cate- 
ue types proper... ii. . ocsos ie CE ch ee ee ae 
Walled (umwallungen) types... .... 87 Unclassified through insufficient data 94 
The factors entering into the production of these various kinds 
of galls are many; a full discussion of them cannot be presented 
here. Attention, however, should be called to the two main groups, 
namely, those which are related to the plant and those related to 
the cecidozoon. The diverticulum galls are, with few exceptions, 
only known from the leaf, particularly the blade, since this organ 
only is sufficiently free from stereome tissues to make possible the 
characteristic pouching out on the side opposite the cecidozoon. 
The walled and concentric types can occur on any part of the plant, 
the latter constituting a much larger aggregation than any of the 
other kinds. Oviposition within the plant tissue or a migration 
inward on the part of the larva is necessary for the production of 
the concentric type of gall. Even in these cases constituting the 
highest galls, plant factors can exert a modifying influence. The 
Study of the relative importance of the two groups of factors 
entering into cecidium morphogenesis in specific cases is one of the. 
most valuable and suggestive in the field of zoocecidology. 
UNIVERSITY OF ARKANSAS 
FAYETTEVILLE, ARK. 
