THE BASIS OF THE DIFFERENTIAL PHYTOTOXICITY OF 4-HYDROXY-3,5-DI-IODOBENZONITRlLE*

Summary. Entry of ioxynil-¹⁴C into portions of leaves was greater with mustard than with barley or pea and was unrelated to stomatal density. Measurement of ioxynil content of sprayed plants showed that by increasing the concentration of ioxynil and adding a surfactant, almost as much ioxynil could be made to enter barley as entered mustard from a lower concentration without surfactant. Auto radiographs showed that a limited amount of ¹⁴C was translocated to a small extent in plants following localized application of ioxynil-¹⁴C. An experiment comparing leaf removal by cutting with destruction of equivalent leaf areas by ioxynil treatment suggested a greater translocated effect of ioxynil with mustard than with pea or barley. Les principes de la phytotoxicité différentielle du 4-hydroxy-3,5-di-iodobetZonitrile II. Absorption et migration     

Cardioaccelerator release in Periplaneta americana (L)

Focal electrical stimulation of the brain of Periplaneta americana evokes the release of a factor with high cardioaccelerator activity. Results of extirpation of components of the retrocerebral complex from an isolated head preparation imply that the corpus cardiacum is the critical component of this system. The cardioaccelerator is a heat-stable proteinaceous compound.