19 ao] WALKER— CYATH US 5 





available nutrition. Figs. 19 and 20 show transverse and longi- 

 tudinal sections of strands. They are made up of many filaments 

 lying almost parallel to each other and surrounded by a few 

 loosely associated branches which form a vague outer sheath. 

 The cells are very long and 2-5 jx in diameter, the larger being in 

 the center. 



• Origin of basidiocarps. — The basidiocarps originate by the 

 slight differentiation and enlargement of terminal portions of the 

 mycelial strands (figs. 9, 10), and are first discernible in cultures 

 as minute white knots on the mycelium (figs. 5, 6). The fila- 

 ments of the strand branch in a fanlike manner at the base of the 

 knot (fig. 10), and on the interior above become more slender 

 (about 2 ju in diameter), much branched, and intricately inter- 

 woven, making a marked contrast with the filaments of the strand, 

 which are larger and little branched. On the outer tip of the knot, 

 however, is a tuft of hairs the same size as the cells of the mycelial 

 strand. It seems evident, from a study of many slides, that the 

 knot originates slightly below the tip of the mycelial strand, that 

 these terminal hairs are the ends of the filaments which formerly 

 made up the tip of the strand, and that the densely interwoven 

 part just below represents the actual primordium of the basidio- 

 carp. This closely interwoven part is very compact toward the 

 lower part and more open toward the top, where large intermycelial 

 spaces appear. 



Early internal differentiation. — The first trace of internal 

 differentiation is the gelatinization of a definite zone of tissue 

 just below the part of the knot which shows the large intermycelial 

 spaces. It extends downward toward the base of the knot in the 

 form of an inverted dome (fig. 11). Fig. 24, between x-x, shows a 

 higher magnification of this zone. The tissue just to the inside 

 of this zone is made up of small, very densely interwoven filaments, 

 and forms the line of demarcation between the primordium of the 

 gleba and that of the peridiurn. The glebal primordium is com- 

 posed of filaments of the same size and general character, but 

 more loosely interwoven, so that large intermycelial spaces remain 

 similar to those found in the earliest stages. Toward the top the 

 filaments become more and more loosely interwoven, and pass 



