486 BOTANICAL GAZETTE [DECEMBER 
of the colloids, which have not been undertaken in this work. 
So far as the results indicate, however, they show no difference 
which would explain curvature on the basis of increased acidity, 
since at the time visible curvature begins the two flanks are of 
equal acidity. 
In testing the natural indicator of the plant, the tissue was pre- 
pared as described above for Vicia Faba; 25 cc. of the filtrate were 
used in titration and several duplicate titrations made. Table IV 
serves to show the accuracy of the titration and to give the color 
reaction. 


TABLE IV 
Tissue used hfe Baglin ” Color unneut. sol. Color neut.-sol. 
Mucor (young) ....| 0.13 | 0.13 | 0.12 | Faintly greenish Color ripe spores 
Wax beans. 2 s3.«.. 0.36 | 0.36 | 0.40 | Opalescent Pale canary yellow 
Rigg apple... t ... 1.61 | 1.65 | 1.60 | Pale cider Dark orange _ 
Lemon juice....... 14.80 |/14.75 |14.75 | Lemonade Color lemon rind 
Lemon rind........ 0.26 | 0.23 | 0.28 | Lemon rind Orange rin 
Orange juice....... 2.12 | 2.18 | 2.14 | Dilute orange juice | Orange rind 
range rind: .. 2. 2. . 29 | 0.30 | 0.30 | Pale orange Deep orange 
Etiolated seedlings— 
igi one aie 0.46 | 0.46 | 0.44 | Faintly yellow Orange yellow 
Sweet peas... ... 0.40 | 0.41 | 0.40 | Opalescent anary yellow 
Sunflower....... 6:93 1.0.23 20 | Dull brownish yel- | Bright greenish yel- 
: low ow 
Vicia Faba..cicc 0.71 | 0.72 | 0.70 | Faintly grayish Color ripe seed 








Neutral red and phenolphthalein were used with the test plate 
as checks in determining the accuracy of the indicator. The 
neutral point is reached when a drop of the alkali fails to produce 
a change of color in the solution. It is interesting to note that the 
color produced in neutralization is usually the color of some part 
of the seed or plant. In Vicia Faba this similarity is striking. 
Solutions of the triturated coat are neutral. The chromogens 
produced in all of the solutions neutralized were precipitated in 
24-48 hours. 
Only one sugar titration has been made. For this analysis 
the etiolated seedlings were grown in sand in the greenhouse at 4 
temperature of about 16°C. When the seedlings were 6-8 cm. 
high, they were geotropically stimulated for 30 minutes and the 
terminal 4.5 cm. used in the analysis. The gathering required 
