The present study concerns the effect of beet seed extract on the cytology of the growing region of onion roots, on the growth of onion roots, and on the germination of seeds of various plant species.

Beet seed extract, in its less dilute solutions, was found to aet as an inhibitor of germination, growth, and mitosis frequency, mainly by its effect on prophase.

The opposite was found to hold for the more dilute solutions, whieh act rather as growth stimulants.

The cytological phenomena, most frequently caused by the extract were contraction and agglutination of chromosomes, explained by the theory of coacervation. C-mitosis phenomena appeared less frequently, and are explained as resulting from the inhibition of the spindle and the inaetivation of the centromere.