The study on the solubility of allelopathic from little iron weed (Vernonia cinerea (L.) Less) in 4 organic solvents, namely diethyl ether, acetone, methanol and distilled water at a ratio of 1:10, 1:20 and 1:40 (dry plant weight (g)/volume (ml)) per root length and a number of roots. It was found that methanol extract had the greatest effect on the reduction of root length and root number compared to other solvents. For the mitotic index, extracts from diethyl ether, methanol and distilled water had a statistically significant reduction in the mitotic index, especially at high extract concentrations (1:10). It was shown that the extract had an effect on the cell division of the onion root tip, thereby reducing the cell proliferation at the root tip.