408 RESEARCHES ON FUNGI 



Whilst the spores on an originally light area are in the early 

 stages of pigmentation, the tint of the area is intermediate between 

 that of a light and that of a dark area. If we wish, therefore, we 

 can speak of three different kinds of areas as making up the mottled 

 hymenial pattern : dark, light, and intermediate. With the 

 microscope it is not difficult to detect intermediate areas here 

 and there : they often mark the transition of a light area into an 

 adjacent dark one. If the reader desires any further details in 

 regard to the general phenomenon of mottling, he should turn to 

 the fuller account given in the description of the organisation of 

 Panaeolus campanulatus} 



Methods for Examining the Hymenium in Surface View. The 

 method described in Chapter II was made use of for the purpose 

 of examining a large area of the hymenium with the low pow r er of 

 the microscope (magnification about 130), i.e. a living gill was 

 mounted on a tiny drop of water in a compressor cell. However, 

 owing to the small size of the basidia and spores, it was found 

 necessary to magnify the hymenium with the high powers of the 

 microscope. Now the gills are pigmented and absorb much of 

 the light passing through them. Therefore, in order to increase 

 the amount of light striking the hymenium when viewed with high 

 powers, the following procedure was adopted. A gill was dissected 

 away from a living fruit-body, wrapped around a finger, and from 

 it a very thin surface-section was taken with the help of a hand- 

 razor. A small drop of water was placed on a glass slide. The 

 section was then mounted on the drop, so that its under sub- 

 hymenial side alone w T as wetted, and then covered with a cover- 

 glass. The result of these operations was that a thin and fairly 

 transparent section was obtained which could not dry up quickly 

 and which possessed a hymenium which looked upwards under a 

 cover-glass without being wetted. The cover-glass only touched 

 and injured certain parts of the section, so that a sufficient amount 

 of the hymenium was left for examination in the normal condition. 

 Strong daylight was directed through the preparation from the 

 mirror. 



The Number and Size of the Spores on Individual Basidia. The 



1 Chapter X. 



