2 BULLETIN 164, U. & DEPARTMENT OF AGRICULTURE. 
It is harmful to wheat seedlings in water cultures, even in such low 
concentrations as a few parts per million, and the plants are killed in 
solutions of 500 parts per million in a few days. 1 The toxic effect is 
less marked upon the tops of the wheat plants than upon their roots. 
Vanillin is also harmful in nutrient culture solutions composed of cal- 
cium acid phosphate, sodium nitrate, and potassium sulphate. It is 
an oxidizable substance and is less harmful in solutions of some of 
these nutrient salts than in others, especially those high in nitrate. 2 
Sodium nitrate and calcium carbonate, 3 which themselves induce 
oxidation, ameliorate the harmfulness of vanillin. 
The isolation of vanillin from soils and its harmfulness to plants in 
aqueous solutions has made a study of its effect in soils and under field 
conditions essential. The results of such experiments with cowpeas, 
garden peas, and string beans will now be given, together with the 
action of vanillin on clover in soil in pots and with wheat plants grown 
in several soils of different characters. 
EFFECT OF VANILLIN ON CLOVER IN POTS. 
An experiment to determine the effect of vanillin on clover was 
made by growing clover in Chester loam soil in large pots. Ordinary 
clay flower pots holding 6 pounds of soil were used. One pot was 
untreated; the other had a total of 300 parts per million of the 
vanillin added to it. 
When the soil was potted, 100 parts per million of the vanillin was 
added and clover then sown, 0.5 gram of seed per pot. The clover 
was sown April 12, and came up well. On April 28, 50 parts per 
million of vanillin were added in solution through a funnel passing 
into the soil nearly to the bottom of the pot, thus avoiding direct con- 
tact with the tops or roots of the clover. On May 15 another 50 
parts per million were added, and on June 1 and June 10, 50 parts per 
million. were added, making the total application 300 parts per mil- 
lion. The experiment was discontinued June 21, 1912. The effect of 
vanillin was noticeable from the first. 
The harmful effect of the vanillin is shown by comparing the un- 
treated pot and the vanillin-treated pot shown in Plate I. The vanil- 
lin-treated plants were healthy in appearance but stunted in growth. 
The green weight taken at the termination of the experiment was 
8 grams from the untreated pot and only 3.8 grams from the vanillin- 
treated pot, a decrease of 53 per cent. 
The soil used in this experiment was a soil of moderate productive- 
ness, and vanillin applied to it at different periods of the growth of 
the plants was distinctly harmful. Other experiments were made to 
i Schreiner, Reed, and Skinner, Bui. 47, Bureau of Soils, U. S. Dept. Agr. (1908). 
2 Schreiner and Skinner, Bui. 77, Bureau of Soils, U. S. Dept. Agr. (1911). 
* Schreiner and Reed, Am. Chem. Soc, 30, 85 (1908). 
