PANAEOLUS CAMPANULATUS 271 



must be admitted that, although the individual elements of the 

 hymenium in Strasburger's illustration have been carefully drawn, 

 yet the real difficulties in the interpretation of their nature have 

 been slurred over. Sachs' illustration for Psalliota campestris will 

 be dealt with when we come to a discussion of the hymenium of 

 that species. A criticism of any other hymenial illustrations is 

 unnecessary, as what has been said already in connection with 

 Strasburger's is practically of general application. In what 

 follows, the author hopes to lay before the reader a more complete 

 account of the hymenium of a Hymenomycete than has ever before 

 been given. 



In investigating the hymenium of Panaeolus campanulatus, the 

 work was begun with a realisation of two important deductions 

 which are based on the already recorded discoveries made with 

 the horizontal microscope. These deductions are as follows : 

 (1) the arrangement of the hymenial elements must have some 

 relation to the coming to maturity of successive generations of 

 basidia, and (2) after the beginning of spore-discharge, the hymenium 

 must become progressively fuller of exhausted basidia. 



The first difficulty to be overcome was the finding of the 

 exhausted basidia elements which previous workers had either 

 neglected or overlooked. A gill was therefore placed in a compressor 

 cell, and the basidia on its upper surface, which were discharging 

 spores, were watched with the microscope. The results of my 

 observations were as follows. A basidium which has just shed the 

 last of its four spores continues for some twenty minutes or half 

 an hour to protrude somewhat above the general level of the 

 hymenium and to display its four stiff, slightly divergent sterigmata 

 (Fig. 93, A, c). At the end of this interval, however, it undergoes 

 two changes, one of which concerns its body and the other its 

 sterigmata. The body of the basidium, in the course of a few 

 seconds, contracts in length, and at the same time its convex outer 

 end sinks inwards towards the hymenium and becomes concave 

 (Fig. 93, A, d, e,f,g; also Fig. 96, x, p. 287). Owing to this change, 

 the sterigmata are dragged into the concavity which has arisen ; 

 they are also drawn nearer together, and their ends, which were 

 originally somewhat divergent, become sharply convergent. If 



