. Comparative morphology of Fungi. Fungi. POLYPORALES 433 If Juel's interpretation is correct, Tulasnella with its sessile basidio- spores germinating in situ is unique in the Basidiomycetes, and does not seem closely related to any other group. If the basidium is con- ceived as developing from an ascus by gradual exogenous spore production, perhaps Tulasnella represents a transitional stage where the spore mass, without secreting a wall about itself, is pushing out of the gonotocont without having reached the stage of a separate entity before it germinates. The very primitive (or reduced) str
. Comparative morphology of Fungi. Fungi. POLYPORALES 433 If Juel's interpretation is correct, Tulasnella with its sessile basidio- spores germinating in situ is unique in the Basidiomycetes, and does not seem closely related to any other group. If the basidium is con- ceived as developing from an ascus by gradual exogenous spore production, perhaps Tulasnella represents a transitional stage where the spore mass, without secreting a wall about itself, is pushing out of the gonotocont without having reached the stage of a separate entity before it germinates. The very primitive (or reduced) structure of the thallus points in this direction. On the other hand, such a conception would indicate that it had not yet reached a suitable mechanism for spore discharge, having lost that of the ascus without having attained that of the basidiospore. A study of the mechanism of spore discharge, as proposed by Buller, to see whether the "conidium" of Juel's interpretation is discharged as a conidium or a basidiospore, would do much to clarify the situation. Vuilleminiaceae.—The only species of this family, Vulleminia come- dens (Corticium comedens) (Maire, 1902), grows on dead oak twigs where. Fig. 275.— VuiUeminia comedens. 1. Germinating zeugite. 2, 3. Young basidia. 4 Mature basidium. 5, 6. Germinating basidiospores. (X500; after Maire,190 2.) it separates the bark from the wood and forms gelatinous corticiaceous crusts to mm. thick. The basidia are formed in the interior of the hyphal tissue and emerge singly at the surface. The hyphae are binu- cleate, the terminal cell of a branch swells, the dicaryon fuses and the zeugite puts forth a slender basidium (Fig. 275, 1) which reaches the open air, broadens considerably at the tip and, after a second nuclear division with transverse spindles, forms four uninucleate basidiospores, in which the nuclei divide and sooner or later a septum is laid down (Fig. 275, 6). Brachybasidiaceae.—The only species of this
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