The leaf structure inPodocarpus brevifolius (Stapf.) Foxw.

Abstract

The family Podocarpaceae (Order Coniferales) is of great interest; its members display a wide range of morphological and structural features in their leaves. In the present study of one of the members,Podocarpus brevifolius (Stapf.) Foxw., the occurrence and characteristics of the transfusion and accessory transfusion tissues are dealt with in some detail and brief notes on stomata are included. The transfusion tissue appears in the form of lateral wing-like extensions on either side of the vascular bundle; the accessory transfusion tissue is a special structural feature extending from the midrib to the margins of the leaf. Both these tissues consist of two types of component cells, the parenchyma cells and the tracheids. They are somewhat isodiametric in the transfusion tissue, while they are long and disposed at right angles to the midrib in the accessory transfusion tissue. The tracheids of the transfusion tissue have bordered pits with circular borders and circular apertures, although oval borders with oval apertures are not uncommon; on the other hand, the tracheids of the accessory transfusion tissue show bordered pits with oval eccentric borders and oval apertures.

The stomata are haplocheilic as in most gymnosperms and amphicyclic. Typically each stoma has four subsidiary cells of which two are lateral and two polar, but this number may often be more than four formed by divisions of the original cells. Some interesting features displayed by the stomata are described and commented upon in the paper.