AbstractThe phytate phosphorus and total phosphorus contents of oat grain have been studied, and it has been shown that there are very significant differences between varieties of Avena sativa on the one hand and of A. strigosa and A. strigosa X A. brevis on the other. The ratio of phytate P to total P is, however, remarkably constant in mature grain. Changes in phytate and total P accompanying maturation of the grain and germination have also been studied. The calcium and magnesium contents of the grain are considered in relation to their presence in phytin, and some of the evidence suggests that the phytin of different cereals may differ in chemical composition.