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 0.1 to 0.2 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 family, Brachybasidium 

 Pinangae, parasitic on the pinang palm in the rain forest of West Java, 

 bears the hymenium erumpent from the stomata as a small granule on the 

 under side of the leaf. As in VuiUeminia, the terminal cells of the hyphae 

 swell to form storage cells, which in this species are united into a small 

 sorus and possess a firm wall (Fig. 276). From time to time such a pro- 

 basidium swells, protrudes its tip above the sorus and becomes a basidium 

 which (in contrast to VuiUeminia) is not swollen at the tip, but bears two 

 sterigmata. As in VuiUeminia, the basidia are chiastobasidia. 



