1913] SCHLEY—GEOTROPIC STIMULATION 483 
in this portion. The cut seedlings were weighed in weighing- 
bottles and the weight obtained by difference. Samples of 6-8 gm. 
were used. 
Immediately after weighing, the samples were cut up fine and 
ground to a pulp in a mortar. Several methods of titration were 
used. In the first method employed, about 50 cc. of distilled water 
were added to the ground-up tissue and the sample titrated at once 
without filtration, using phenolphthalein or neutral red as indicator. 
The objection to the method is that reaction between the acid yet 
in the tissue with the alkali is slow yet continuous, so that the end 
point is not definite. A second method used was the test plate 
method: The tissue was ground as before, filtered through glass 
wool, and the filtrate refiltered through asbestos over a filter pump. 
The tissue together with the glass wool filter was again triturated 
and washed quantitatively into the filtrate previously obtained 
and the vo'ume made up to 100 cc.; 10 or 25 cc. were used in a 
titration and the average of several titrations used in calculation. 
The end point was determined by means of phenolphthalein in the 
following way. Two solutions of phenolphthalein were prepared. 
The first was prepared by adding 10 drops of an alcoholic solution 
of phenolphthalein to 25 cc. of distilled water. The second solu- 
tion contained in addition 3 drops of a n/20 solution of NaOH, 
enough to make the solution a decided pink color. A few drops, 
of each solution were placed on a test plate and the sample being 
’ titrated tested by introducing a small quantity on the end of a small 
stirring rod into each of the solutions of phenolphthalein. The 
end point was reached when the sample introduced just failed to 
neutralize the small amount of alkali in the one solution, as indicated 
by the faint pink color remaining, and just showed a faint pink 
tinge in the other solution. In this way the end point was not 
obscured by the color of the solution. The method finally adopted 
was that of using the natural indicator in the plant itself. It has 
been observed in the course of both animal and plant tissue est 
sis that chromogens develop when certain fractions, as the race 
fraction, are neutralized. This suggested the idea that possi 
the raw material upon neutralization might show a change of co 
which could be used as an indicator. The reliability of the natura 
