412 COMPARATIVE MORPHOLOGY OF FUNGI 



fundaments are differentiated in two directions, as sterile organs and 

 basidia. 



In the hyphal ends destined for sterile organs, the nucleus of the ter- 

 minal cell degenerates. According to their further relations, they may 

 be divided into paraphyses and cystidia. In the development to paraph- 

 yses they increase in width, and serve to keep the basidia apart and, by 

 their elongation, to aid in the expansion of the pileus. 



In the development to cystidia, they elongate greatly (even reaching 

 a length of 0.2 mm.), rise far above the hymenium, then swell greatly 

 (Fig. 294, 1) and often are covered with slimy excretions or with crystals. 

 They are distinguished from paraphyses by their peculiar form and smaller 

 numbers. Usually they may be traced back deep into the tissue layer 

 and are probably located at the ends of the "vascular" system; occasion- 

 ally they may be only basidia whose reproductive function has been 

 hindered by oily and fatty substances. Their walls are occasionally 

 thickened (except at the tip). Their form is very variable but usually 

 constant for a given species (Demelius, 1911). Their function is still 

 unknown. Knoll (1912) held them to be hydathodes, which give off the 

 end products of their metabolism in the form of drops of liquid. Levine 

 (1913) laid more stress on the slimy property of the drops of liquid, as 

 often drops of water may be given off from any portion of mycelium of 

 fructification (Merulius!) . He held them to be druses similar to the druses 

 of higher plants. In any case, it is notable that the gel given off from 

 larger groups of cystidia is visible to the naked eye. In the course of 

 their development, the cystidia in certain families, e.g., the Coprinaceae, 

 seem to have undergone a change of function and no longer serve excretory 

 but rather mechanical functions, especially as supports of the lamellae. 

 Special forms of cystidia with oily, granular content are called gloeocys- 

 tidia. Observations on Sebacina gloeocystidiata show curious bands of 

 deeply staining material along the cell wall, after the nucleus has com- 

 pletely disappeared (Kuhner, 1926). 



In the development of the basidia, the dicaryon of the terminal cell 

 fuses (as in the young ascus) to a single large diploid nucleus. The 

 terminal cell functions as a zeugite, just as the hook cell of an ascogenous 

 hypha (e.g. the terminal cell of the Plicaria type). It elongates and 

 becomes a basidium. In many species, this development proceeds very 

 irregularly so that mature basidia are frequently intermixed with young 

 ones and the usual hyphal ends. These latter, although they are only 

 undeveloped basidia, have been erroneously called paraphyses in system- 

 atic literature. 



The basidia may be divided into several types according to the 

 peculiarities of their further development. The basidia in which nuclear 

 division is not followed by formation of septa are called auto- or holo- 

 basidia. In the first type they are mostly cylindrical, elongate con- 



