BY G. P. DAUNEr,L-SMITH. 885 



eventually perishes. "Virgin spawn" obtained fiom tlie fields is, 

 therefore, transferred to beds of manure, wliere it spreads and 

 supplies the grower with a "frank spawn" for growing the edible 

 mushroom. But "often twelve to fifteen kinds of vii-gin spawn 

 as found in the fields or on heaps of refuse are discarded as use- 

 less before a good strain is obtained "(2). That the production 

 of inverted caps was a feature inherent in the spawn under dis- 

 cussion, is shown by tlie fact that all mushrooms developed from 

 it produced abnormal caps, whereas mushrooms produced fiom 

 other spawn, under identical conditions, did not. 



This phenomenon, together with the characters of the spoi"0- 



phores, lends support to the hypotheses that have been put 



forward as to the evolution of the cap, and as to the probable 



origin of the Agaricaceie, which may be stated briefly as follows: 



(a). Evolution of the ca-p 



1. The production of the horizontally extended, llatteued cap- 

 form of fruit from an original, cylindric, dome-shaped form. 



2. The relegation of the hymenial tissue to the lower surface 

 of the cap. 



3. The formation of "gills " from the original pore or alveolar 

 structure. 



(6). Evolution oj the Agaricacea^. 



The most primitive type of fructification is probably that of 

 Glavaria, in which a cylindric or club-shaped branch is uniformly 

 covered with hymenium, which extends down the stalk as well 

 for some distance. 



"Cases in which the hymenium covers the whole of the upper 

 exposed surface, in the form of a semi-alveolar structure, or 

 labyrinthiform gill-formation, are seen in Tremella and Ncema- 

 telia, and these plants pertain to the Protobasidio-Mycetes; the 

 Tremellinese have, according to Maire's classification, branched 

 off laterally from the Auriculariacese, and it is from these latter 

 that the Agaricacese and Polyporace?e have descended. 



In this connection, it is interesting to note that, in one of my 

 specimens that was fairly large, but was obtained in the "button- 

 stage" before rupture of the velum, the whole of the upper surface 

 of the cap is covered with sporogenous tissue (PI. xciii., fig. 9). 



68 



