540 BOTANICAL GAZETTE [JUNE 
internode, ovulary, etc.) as a unit suffers modification without a 
fundamental change in its morphology. The “histoid”’ galls are 
those more numerous types in which an entire plant organ is not 
involved, the gall being more or less definitely appendicular. This 
group includes all of the prosoplasmas and part of the kataplasmas. 
DATA BASED ON NUMBER OF CHAMBERS 
BEOMOLERIAINONS BONG eG So. CG AR oe 408 
Polvthelamons palis so ie ee aie he ie a 134 
PEON COMIUEIIED BOEIS oe a be, ck ah dw ee ee 67 
Sueiicient ate (0 CAM oo i es oc ae eg as 183 
The excessively large number of monothalamous forms is a fact 
related to the character of oviposition. If the eggs are habitually 
deposited in an aggregate manner, a polythalamous gall is almost 
certain to result, although there are striking exceptions to this. 
The great majority of larvae, however, begin their gall-making 
activity at sufficient distance apart to develop the common mono- 
thalamous types of cecidia. 
KATAPLASMAS AND PROSOPLASMAS 
a pene Cea Dia a ORGY eo etme ted eee pneu ee 395 
EVOUMNMIIIN Sor ie vista oh Le eC os ds Vie mes Sas ee ees 322 
TRGUUAenE MUR 80 CORN ye ee cs 73 
Viewed from an evolutionary standpoint, the kataplasmas 
represent the lower levels and the prosoplasmas the higher. That 
the latter have undergone a considerable expansion indicating 
relatively rapid progress in recent geologic time is evidenced by the 
relatively large number of prosoplasmas. 
ORGANOID AND HISTOID GALLS 
NUN a er a 215 
PROM ih er kV 8 ey Cabo een i bcs a os wis 495 
LOMO, ALE OO CANE a 82 
These figures have no special significance, perhaps, other than 
the indication of differences in the range of the gall stimulus. In 
the organoid types the stimulus is diffused over relatively large 
areas, inciting all of the tissues of one organ to hypertrophy and 
hyperplasia. In the histoid forms the stimulus only affects those 
tissues in a restricted area about the cecidozoon, these tissues 
responding in a definite and striking manner. 
