MUSHROOMS AND TOADSTOOLS 



249 



continued directly upward from the strand. Of these tissues, the 

 medullary bundle spreads out at its upper end and forms a dense 

 sheaf-like head by repeated branching and anastomosing. The 

 cortical layer of tissue becomes the outer wall of the volva; the sheaf- 

 like head gradually differentiates into all the other parts of the older 

 egg. In such differentiation the central 

 column first appears. The formation of 

 the gelatinous layer of the volva now begins 

 in the periphery of the head. A dense 

 dome-shaped mass arises. Along the inner 

 surface of the dense zone and next to the in- 

 termediate tissue, the rudiment of the gleba 

 arises from the clustered swollen ends of 

 lateral branches of the tramal tissue. These 

 hyphal ends take position in a palisade 

 layer facing the intermediate tissues and by 

 the crowding in of new hyphal ends (basidia) 

 the surface of this layer becomes greatly 

 enlarged and thrown into folds and torn 

 from the intermediate tissue. The rudiment 

 of the stipe arises in the intermediate tissue 

 lying next to the central column by the forma- 

 tion of deeply staining tissue rich in proto- 

 plasm. Somewhat later, masses of tissue in 

 the dense and intricately interwoven rudi- 

 ment of the stipe show a tendency toward 

 gelatinization. These masses mark the 

 position of the later chamber-cavities in the 

 wall. Toward the upper end of the stipe, 

 such masses are in contact with the central 

 column, and they mark the position of the 

 pits which open into the main central cavity 

 of the stipe in mature stages of M. can in us. 



The chamber walls are thrown into folds through a more rapid growth 

 of the pseudoparenchyma than that of other parts of the egg. Final 

 elongation of the stipe and elevation of the gleba is brought about 

 through the straightening out of the folds in the chamber walls. 



The studies of Atkinson deal with the origin of the veil of Dictyo- 



FiG. 99. — Mature stink- 

 horn, Diclyophora duplicata. 

 {Photo by W. II. Walmsley.) 



