Abstract
Nodal roots of field specimens of S. nutans (L.) Nash exhibited Si deposition confined exclusively to the endodermis in the form of nodular silica aggregates. Si distribution in this species is compared with that for other genera within the tribe Andropogoneae, and the possible function of Si in the root is discussed. P. communis Trin., in contrast, exhibited no consistent accumulation of Si in the nodal root. The variations in Si accumulation between the 2 spp. are interpreted in relation to their root anatomy and differing habitat characteristics.