Silicification of Bulliform Cells in Grasses

Abstract

SOME of the opal phytoliths in the fine sand fractions of certain British soils have been traced to the grasses Sieglingia decumbens and Molinia caerulea ¹ and it now appears that the largest of these arise in the bulliform cells of these species. As obtained from the soil or in residues prepared from the leaves, they appeared with fan-shaped outlines (Fig. 1), or with rectangular outlines, rather tabular but thinning to one edge, their surfaces often carrying one or two parallel ribs (Fig. 2). Using methods previously described², we have observed similar bodies in situ in the bulliform cells of Chusquea culeou (Figs. 3–6) and Brachypodium pinnatum. The arrangement of bulliform cells resembles in many ways the architecture of a long semicircular arch (Fig. 7), the upper blocks having the broadest and most fan-like section (A, A′). In the plant the units (that is, the cells) are unequal and the long ones may be pressed out as ribs at each junction between units in the next row (B, B′). As it is unusual for adjacent cells to be silicified, the phytolith surfaces may be curved due to the bulging of neighbouring cells (Figs. 1, 6, 7A″).