All crops studied were injured by sufficiently high concentrations of Al if this was supplied alternately with P, and in a culture solution of an acidity which would not precipitate the Al. Crops most sensitive to Al were lettuce, beets, timothy, and barley. Medium sensitive crops were radishes, sorghum, cabbage, oats, and rye. Corn, turnips, and redtop were noticeably resistant, redtop being the most resistant of the 3. Tendency of crops to change the solutions toward a more alkaline or more acid reaction was not correlated with sensitiveness toward Al. The 1st evidence of toxicity of Al was dwarfing and injury to roots, accompanied in corn plants by reduced absorption of dyes, nitrate, and water. As indicated by the haematoxylin test, the Al absorbed by the plants accumulated in the cortex, mainly in the protoplasm, and was concentrated in the nuclei. No accumulation of Al was detected in any other parts of the plants.