156 BOTANICAL GAZETTE [auGusT 
law applies in geotropism as in various tropic responses. GILTAY devised a 
special centrifuge with a vertical axis for testing this point. He finds that with 
the average of 368 tests, with the angle of the resultant approximating 45°, the 
primary root fell 2.1° below the resultant. This deviation can well be accounted 
for by the variation in speed of rotation and the variation of roots themselves. 
This seems to furnish evidence for the identity in nature of the geotropic and 
centrifugal stimuli WILLIAM CROCKER. 
Réle of hydrocyanic acid.—Treup® has found that the amount of hydro- 
cyanic acid in plants of Sorghum increases during the day, not due to the direct 
in the young leaves and gradually diminishes as the leaves grow older. With 
Sorghum, young leaves grown in a dry season or on dry soil contain much acid, 
and for this reason are dangerous as food for stock. Leaves about to fall contain 
very little acid, while, with only two exceptions, those already fallen contain none. 
Gurcnarp found that fallen leaves of Sambucus nigra contain much of the acid. 
TrEUB confirms these results and finds the same to be true of fallen leaves 0! 
Indigofera galegoides. The hydrocyanic acid is probably the first recognizable 
simple organic product of the assimilation of nitrogen, and perhaps the first 
organic nitrogen compound formed. The amounts of the acid in plants watered 
with a solution of sodium and potassium nitrate increased or decreased i pro- 
portion to the amount of nitrate used. RAvENNA and Pett think that nitrates 
and carbohydrates are necessary to the formation of the acid. TREUB 4 
with these conclusions, and adds that dextrose is especially essential. The 
acid probably does not occur in plants as such, but in the form of a glucoside from 
which it can be liberated by an enzyme or by boiling water.—R. CATLIN RosE. 
Parasitic flagellates in plants——Although rapid progress in the study of 
parasitic flagellates has shown them to be of widespread occurrence in an *e 
organisms, the discovery of these parasites in plants is a noteworthy fact. Th 
occurrence of a trypanosome-like parasite in the latex of Euphorbia age” 
Mauritius was first reported by Laront.'? The discovery was S0oD afte 
° TrEuB, M., Nouvelles recherches sur le réle de l’acide cyanhy driqne OM 
les plantes vertes. Ann. Jard. Bot. Buitenzorg II. 8:84-118. 1910. \ 
70 Lafont, A., Sur la présence d’un parasite de la classe des Flagellés sao 
latex de /’ Euphorbia pilulifera. Compt. Rend. Soc. Biol. 66:1011-1013- 199° 
