406 RESEARCHES ON FUNGI 



I shall now endeavour to explain the organisation of the 

 hymenium of the Mushroom in detail, and the reader will find 

 that it is essentially the same as that of Panaeolus campanulatus 

 and Stropharia semiglobata. However, the hymenial elements 

 of the Mushroom are very much smaller than those of these two 

 species, and their investigation has therefore been proportionally 

 more difficult to carry out. 



The Mottling of the Gill Surface. The hymenium covering the 

 exterior of each gill which has become outstretched is finally mottled 

 with small lighter and darker areas (Fig. 134, B, p. 377). The 

 pattern is similar to that already described for Panaeolus campanu- 

 latus and Stropharia semiglobata, but finer. This relative fineness 

 is in part due to the fact that the diameter of the basidium of a 

 Mushroom is only about one-half that of the basidium in the other 

 species. If a dark area of a Wild Mushroom be examined with 

 the microscope, it is found to possess a large number of basidia, 

 each of which is bearing four spores which have already become 

 pigmented. The darkness is simply due to the colour of the spores. 

 The light areas, on the other hand, contain basidia which are just 

 about to develop spores or which bear spores which may or may 

 not have attained full size but are still unpigmented. The relative 

 lightness is due to the absence of spore- wall pigment. 



With the help of the microscope, one finds that the light and 

 the dark areas are irregularly shaped and very variously arranged 

 in respect to one another. A semi-diagrammatic drawing of the 

 hymenium of a Cultivated Mushroom, in which are shown only 

 the spores and the basidia which have produced them, is repro- 

 duced in Fig. 142. Here we see a light area surrounded by a dark 

 area. The dotted contour-line indicates the limits of the former, 

 while the arrows point to the directions in which the line is being 

 pushed. Just outside the line, the spores on the dark area are 

 being gradually discharged, while just inside it new basidia are 

 coming to maturity and producing spores, so that as the dark area 

 becomes reduced the light area becomes extended. There are 

 such waves of development passing over the hymenium in a very 

 irregular manner in all directions on every gill. In the course of 

 a few hours, every dark area, owing to the discharge of its spores, 



