Introduction

Duportella is a small genus containing five species. It was separated from Hymenochaete by Patouillard because of the false setae present in the hymenium, which replace the conspicuous thick-walled setae of the latter genus. False setae (termed pseudosetae herein) are formed from free ends of context hyphae, upturned to form a palisade in the hymenial layer, either preceding, accompanying, or following development of basidia and paraphyses.

Hymenophore. Species may be pileate, umbonate-sessile, or resupinate. Pilei are either conchate and attached by a narrow vertex (D. fulva), effused-reflexed upturned margins of broadly resupinate areas (D. fulva, D. monomitica), umbonatesessile with plane free margins as in most fructifications of D. monomitica, or resupinate (D. fusispora, D. sphaerospora). Fructifications usually develop first as numerous scattered colonies. These may become free at the margins and expand to form conchate pilei attached by a narrow vertex as in some collections of D. fulva; or more usually merge to form broadly effused areas extending for several cm. From margins of the latter, effused-reflexed pilei may develop (D. fulva), or arise from the upper edges alone of fructifications growing upon upright trunks or branches (D. monomitica). The pileus surface is clothed with abhymenial hairs which may form a tomentum (D. monomitica), differently coloured radiate brown bands (D. fulva), or in old plants of the latter species be imbricate so that the surface appears silky.

Context. Composed either of an intermediate tissue of parallel hyphae turned into the hymenial layer (D. fulva, D. monomitica) or of hyphae mainly upright (D. fusispora, D. sphaerospora), the context is without a cortex, so conspicuous a feature in most pileate species of Stereum and of Hymenochaete species placed under Section 1. Abhymenial hairs arise from the intermediate tissue; they are always present in pileate species, but absent from or rudimentary in those which are resupinate.

Both dimitic and monomitic hyphal systems are present. Fructifications of D. monomitica are formed from generative hyphae alone; other known species are dimitic, composed of generative and skeletal hyphae. Coloured some shade of brown, and usually thick-walled, skeletal hyphae are sparingly septate and sparsely branched. In species with a dimitic hyphal system generative hyphae are thin-walled, hyaline, freely branched and possess conspicuous clamp connexions. Generative hyphae of the monomitic species D. monomitica are brown, thin-walled, branched, septate, and

without clamp connexions. They branch in a distinctive manner; each branch arises beneath a septum, emerges at a wide angle, then turns parallel with the parent hypha (Text-fig. 4).

Hymenial Layer. Basidia are subclavate, project, and bear 2 or 4 spores on slender sterigmata. Paraphyses are subclavate, shorter and narrower than the basidia, and arranged in a dense palisade. Spores are elliptical or suballantoid in three species, fusiform in D. fusispora, and globose or subglobose in D. sphaerospora.

The hymenium develops early in D. fulva and D. sphaerospora, appearing before most of the pseudosetae; in older plants basidia and paraphyses disappear, to be replaced by a close palisade of pseudosetae. In D. tristricula (Talbot, Bothalia, 6, 47, 1951) and D. monomitica pseudosetae first form a dense palisade which gives the surface its dark colour. Subsequently basidia and paraphyses appear, at first in scattered groups buried among the pseudosetae, later forming a continuous palisade when the surface colour changes to cinereous-or ochre In D. fusispora pseudosetae and basidia appear to develop simultaneously, pseudosetae forming a dense palisade below the basidial layer, with a small number, projecting above its surface.