BROOKLYN BOTANIC GARDEN MEMOIRS 
(d) Galls with very definite and distinct strata of gall 
tissue—parenchymatic, vascular and _ protective, 
e. g., cynipid galls. Kiister’s prosoplasmatic galls. 
Many insect galls differ from crown galls in that 
(1) the parasites are few or reduced to a single 
organism, and (2) are extracellular, whereas in crown 
gall the parasites are more numerous and are intra- 
cellular. Many differences in structure, even of the 
more complex galls, can be explained, I think, 
by these two differences, especially if we assume 
(3) that the kind of reaction depends on the volume, 
direction, and velocity of the stimulus, its constant 
or intermittent flow, and on location, distance, 
and mobility or immobility of the source of the 
stimulus. As in various insect galls so in crown 
galls, there is a tendency toward the production 
of more primitive tissues and of various anomalously 
formed organs. 
III. Crown galls are formed by extrusion of chemical substances. I have 
recently produced galls with diluted crown-gall products and 
this, it seems to me, suggests a new method of attacking gall 
problems in general, especially those in which the gall para- 
sites can be cultivated pure in sufficient quantity for chemical 
analysis, e. g., various fungi. Striking results have been ob- 
tained but many tests are yet to be made with the crown-gall 
substances in various dilutions, mixed and separate on a variety 
of tissues of responsive ages. Various types of cell growths 
have been produced by the action of ammonia, acetic acid, 
formic acid, aldehyd, etc. (all products of Bacterizim tumefaciens, 
the crown-gall organism) in less than killing doses, that is, 
various degrees of hypertrophy and hyperplasia of cells and 
mixtures of the two have been observed. Sometimes there is 
great stretching of cells as in certain fungous and insect galls. 
Giant cells in the animal pathologist’s sense of that word, 
namely, cells containing several to many nuclei, such as occur 
in the common nematode galls, are to be searched for in all 
sorts of plant galls and to be produced, if possible, experi- 
mentally, 7. e., with gall-forming substances. In due time we 
shall be able, I believe, to get these multinucleate cells at will. 
Probably they are weakened cells. “Two very important things 
to be determined are whether the size of the cell depends on 
the volume or rate of movement of the stimulus or on the 
kind of stimulus, and whether mixed stimuli applied in varying 
proportions change the manner of cell reaction. 
