In this article we will discuss about the classification of geoglossum.
Family Geoglossaceae:
This family was formerly associated with the Helvellaceae to form the order Helvellales, before the importance of the type of dihiscence of the asci became apparent. The fruiting bodies are mostly found on rotton wood, decaying leaves, moss orsoil, usually where plenty of moisture is available.
They are long-stalked, club-shaped, fan-shaped or pileate, more rarely discoid or turbinate varying from a few millimetres to five or more centimetres in height. Several genera have bright-coloured fruiting bodies, while those of others are black.
The hymenium either forms a closely adherent layer to the somewhat thickened upper part of the stipe or forms the upper surface of a head borne at the apex of the stipe. The fruiting body may be entirely made up of hyphae or the cortex may be pseudoparenchymatous.
The hymenium usually covers only a part of the fruiting body but in some cases extending over the whole of it or the hymenium may occupy the upper surface only. The fruiting bodies are usually elastic or fibrous rather than brittle, a few leathery, others are distinctly gelatinous.
Asci are with distinct paraphyses. The ascus contains eight ascospores and opens by the ejection of a plug. The ascospores are ellipsoid and one- or two-celled or long elliptical to filiform or narrow several to many septate. They are hyaline to smoky to dark brown.
Genus Geoglossum of Geoglossaceae:
This is the largest genus in the family Geoglossaceae. It grows on rotten wood, log, stumps; on wet ground: or among leaves or rich humus. Fruiting bodies are fleshy, erect, stipitate, clavate (Fig. 239A-D), hymenium covering only the upper portion, black or brownish black, commonly known as “earth-tongues”.
The terminal fertile region becomes club-shaped, laterally compressed, or forming a cup, or a pileus. In some of the simpler forms, as in Geoglossum hirsutum, there is no clear line of demarcation between the fertile and sterile regions. The genus Geoglossum is separated from its closest genus Trichoglossum by the absence of setae from the hymenium.
The fruiting bodies arise as a tangle of closely twined hyphae which are elongated at the periphery and entirely surrounded the tangle. In the middle of the base, however, they are more rounded or polyhedral. The middle cells elongate upwards and thus cause the elongation of the whole fruiting body, while the basal cells remain irregularly angular with thickened walls.
The ascogenous hyphae push from the ground tissue and form asci. The sexual organs undergo a peculiar degeneration. Antheridia are lacing; the nuclei in the ascogonia are arranged in pairs and migrate into the ascogenous hyphae. Thus the sexual processes are autogamous.
Asci are unitunicate and inoperculate; cylindric-clavate, pore turns blue with iodine, and 8-spored (Fig. 239E & F). Ascospores are cylindric-clavate, brown, multi-septate lying parallel in the ascus (Fig. 239E & K). The ascospores are apt to protrude from the ripe asci giving the hymenium a downy appearance.
Paraphyses are numerous, slender, septate, slightly longer than the asci, may be abruptly swollen at the tips or cells may be swollen to give a beaded appearance (Fig. 239G & J).
Some Indian species of Genus Geoglossum of Geoglossaceae:
Geoglossum alveolatum Durand; G. hirsutum Pers.; G. ophio- glossoides (L.) Sacc.