INTERNAL SECRETORY STRUCTURES IN HYPERICUM (CLUSIACEAE) - HYPERICUM-PERFORATUM L AND HYPERICUM-BALEARICUM L

Hypericum species have translucent oil cavities; many species also have superficially similar black internal structures. Contradictory descriptions of both structures emerged from 19th century studies, which we review here. Our study of Hypericum perforation L. leaves and petals shows typical schizogenous translucent oil cavities that develop with a uniseriate epithelium. Black structures, in contrast, are nodules, each composed of several large cells lacking a central intercellular space and surrounded by a biseriate sheath of flattened cells. Nodule cells accumulate black, granular, but non‐resinous contents. The ‘streaks’ that traverse petals are elongate tubular cavities or nodules, except for some chimerical tubes composed partly of each. Hypericum balearicum L. leaves have bulging, pustular cavities. A large cellular nodule forms first, by non‐synchronous cell divisions within the leaf mesophyll, and is surrounded by a sheath of two to three flattened cell layers. The central cells then separate unevenly to form an irregular cavity into which isolated cells and clusters of cells intrude, some of which continue to divide as other cells degenerate. Little or no oil accumulates in the cavity, and the peripheral lining of cells is very irregular to flattened and empty. Both species studied exhibit secretory structures with previously undescribed anatomical features. Copyright © 1990, Wiley Blackwell. All rights reserved