I9I9] 



WALKER— PLUTEUS AND TUB ARIA 



ends on the surface. These filaments are sHghtly larger than those 

 of the stipe, often reaching 4 ^i in diameter at their ends. This diver- 

 gent growth of the hyphae making up the primordium of the pileus 

 is similar to that described by De Bary (12, 13, 14) for Nyctalis 

 asterophora, N. parasitica, and CoUybia dryophila, and by Blizzard 

 (11) for Omphalia chrysophylla, Clitocybe adirondackensis, C. cerus- 

 sata, and Clitopilus noveboracensis. The primordium of the 

 hymenophore (fig. 29) consists of only a slight modification of these 

 outward turning filaments such as cover the pileus and stipe. They 



Fig. I 



Fig. 2 



Figs, i, 2. — Fig. i, A, diagram showing plane of sections shown in figs. 9-11; 

 B, small arrows showing direction of growth in hymenophore of same basidiocarp; 

 fig. 2, diagram of plane of sections shown in figs. 19-22. 



are more closely packed together, smaller, and with slightly denser 

 protoplasmic content. 



Figs. 2-8 show median and tangential longitudinal sections of 

 young basidiocarps in successive stages of development. In the 

 fruit body shown in figs. 2 and 3, and more highly magnified i/i 

 figs. 30 and 31, a definite palisade layer has been formed, and the 

 loosely interwoven outer portion of the stem is more pronounced; 

 otherwise the structures show no further differentiation. As 

 growth progresses the margin of the pileus shows a strongly epinas- 

 tic development, so that as the pileus enlarges the margin turns 

 abruptly downward (figs. 4, 6), while the hymenophore still remains 

 in the palisade condition, as shown by figs. 5 and 7. The continua- 

 tion of this epinastic development causes the margin of the pileus 



