Opaline Silica in the Inflorescences of Some British Grasses and Cereals

Abstract

Opaline silica depositions in the inflorescences of native grasses and cereals grown in Britain are described. Methods of preparation are given, and opals are figured and classified according to shapes and disposition in the bracts. Resemblances to opals in the leaf, particularly the sheath, are recognized; but two forms found in some leaf-blades, namely costal opals in the ‘long silica cells’ and bulli-form opals are not present in the bracts. Opals develop first in ‘short silica cells’. Later, profuse dendriform opals may develop in long cells which have earlier been heavily lignified, particularly in the lemmas of the Hordeeae, Brachypodieae, and Bromeae, the opal presumably affording additional protection to the grain.