174 
Journal of Agricultural Research 
Vol. VIII, No. 5 
(osmosis-inducing) purely physical effect, in which case many other sub¬ 
stances would cause it, even in great dilution, and there would be then, 
also, no evidence of any wounding of the tissues except in case of exces¬ 
sive doses. 
These various inquiries formed the basis of further experiments. 
First, I tested out in Ricinus stems, and in part also in young green 
tomato fruits the effect of the following compounds: Urea, ammonium 
carbonate, ammonium tartrate, ammonium citrate, ammonium malate, 
ammonium acetate, ammonium sulphate, ammonium sulphite, ammo¬ 
nium nitrate, ammonium lactate, ammonium chlorid, ammonium oxa¬ 
late, ammonium formate, ammonium salicylate, ammonium succinate, 
dibasic ammonium phosphate, and monobasic ammonium phosphate, 
with generally positive results and often very striking ones, and also 
once in case of the last-mentioned substance with very unexpected struc¬ 
tural transformations to be described later. 
To return now to the individual action of the various salts of ammonia. 
I obtained in the pith cavity of Ricinus and in the interior of green tomato 
fruits striking proliferations with a variety of these salts, as may be seen 
by consulting the accompanying plates, and that too whether the tissues 
were or were not visibly injured. Some of these substances at first 
were used too strong and exerted a local killing effect, but remote from 
these wounds fine proliferations were obtained from the apparently un¬ 
injured surface layer of the pith in Ricinus stems and from the inner peri¬ 
carp wall in the green tomato fruits. Special attention is called to the 
outgrowths on the uninjured inner face of the green carpels of the tomato 
as a result of the action of ammonium carbonate (PI. 6, fig. i and 2) am¬ 
monium acetate (PI. 6, fig. 3), and ammonium tartrate (PI. 7,8,9, and 15). 
The relatively small size of the cells in Plates 7 and 8, as compared with the 
excessively large cells figured by Dr. von Schrenk from his cauliflower 
intumescences, need not excite comment, since in Plate 9 and also further 
on we shall see that the cells of the intumescences which I have produced 
while often smaller are also sometimes much larger than corresponding 
normal cells of the plant and frequently vary among themselves within 
wide limits, even in the same intumescence, just as they do in bacterially 
induced crown galls. It also appears to make a difference what chemical 
is used or else different volumes of the same substance act differently, 
large cells being formed under one stimulus and small cells under another 
stimulus. 
Serial sections cut from green tomato fruits exposed to the ammonium 
tartrate show that the internal proliferations have arisen in many cases 
at least from a single-layered epithelium in which and under which there 
is no evidence of wounding. In the same way under the numerous pro¬ 
liferations obtained on tomato carpels with the ammonium acetate I 
could find no evidence of any cell injuries. In the strengths used the 
