Barley, wheat, and cotton seedlings grown in low and high pHospHate culture solutions showed a decrease in top-root ratio with increase in pHospHate concentration. Corn root tips were then grown in sterile culture solutions of low and high pHospHate concentration. Greater average elongation and a greater number of secondary roots developed in the low pHospHate medium than in the high pHospHate medium. It is concluded that the increased development of roots of plants, due to increasing pHospHates, is not the result of a direct stimulation of cellular activity in the roots but rather a translocation to the roots of growth stimulating compounds or simple substances formed in connection with the pHotosynthetic activity of the tops.