1922] Essig: Morphology of ScMzophifllum commune Fries 451 



lead to entirely erroneous interpretations of the structure of the sporo- 

 phore. Thus sections cut obliquely through specimens with well devel- 

 oped "gills" which can be seen unmistakably with the unaided eye 

 appear as though the hymenium lined a series of chambers, or as if 

 the "gills" in the middle of the section were normal, with "hymenial 

 chambers" at each edge. Certain sections cut in this manner corre- 

 sponded in many ways to figures given by Adams (1918). Material 

 for young developmental stages was sectioned from 20 to 25/x in thick- 

 ness so that the sections would remain entire. For cytological work 

 the sections were cut 5 and 10 micra thick. Sections as thin as 5 micra 

 will not hold together well, so that, for the finer structure, it was neces- 

 sary to use only fragments. 



Flemming's triple stain was used for some sections, but was not so 

 satisfactory as safranin alone. Using a two-minute period in a 3 per 

 cent solution of safranin in 50 per cent alcohol and washing out rap- 

 idly, a fair differentiation was obtained. The nuclei stain deep red, 

 the cytoplasm a very light pink, and the cell walls an intermediate 

 shade. All efforts to make the nuclei stand out more clearly by coun- 

 terstaining resulted in failure. For staining spores, a 48-hour period 

 was needed, as in a shorter period the stain would be almost entirely 

 removed in the washing-out and dehydrating operations preceding 

 clearing and mounting. The sections and spores were cleared in xylol 

 and mounted in Canada balsam. 



III. MORPHOLOGY 



1. GENERAL CHAEACTEEISTICS OF THE SPOEOPHOEES 



Schizophyllum is distinctly a xerophyte. The sporophores are 

 found in either of two conditions : 



1. In dry weather the sporophores are desiccated, hard, and some- 

 what brittle (fig. 1, pi. 51). The margin of the pileus is curved inward, 

 decreasing the width of the sporophore about 25 per cent. Each 

 hymenial plate is incurved on the side toward the hymenium. The 

 hymenial surface is hidden and protected. Only the villous sterile 

 surface of the hymenial plates can be seen from the lower side. There 

 is no discharge of spores. This is an inactive period. 



2. In moist weather the sporophores take up water and become 

 flexible and leathery in consistency. The pileus margin is only slightly 

 curved downward. The gill plates unroll and extend vertically down- 

 ward, or nearly so (fig. 2, pi. 51). Spore discharge begins about an 



