(6,7,16,18,21). In a recent paper, Outlaw et al., (18) presented a qualitative description of phosphate distribution within Vicia faba leaves, and showed, by x-ray microanalysis, that phosphorus is more abundant in guard and epidermal cells than mesophyll cells.Histological staining and microsurgical separation of cell types, followed by enzyme specific assay, showed that phosphorus was present predominantly as Pi. In earlier work, low phosphorus contents of mesophyll cells of Atriplex (28) and Puccinellia (27)