262- RESEARCHES ON FUNGI 



by means of corks and pins. The pileus was prevented from 

 altering its position by being placed in contact with the crystallis- 

 ing dish above ; and the stipe was held by two black-headed pins 

 fixed to the two large circular corks and by three darning needles 

 coming from the pieces of sheet cork (Ck) which had been attached 

 to the side of the dish by means of sealing-wax. A circular glass 

 plate (GP), from which a piece of the glass had been removed 

 at the edge, was then obtained. For the piece of glass broken away 

 a very thin sheet of cover-glass (Cg) was substituted, the attach- 

 ment to the inner side of the thick glass plate being effected with 

 the aid of melted paraffin wax. The glass plate was then set in 

 front of and against the crystallising dish, so as to close it, except 

 for a small space (V) which was left for ventilation. The plate 

 was arranged so that it rested on the stand (S) and so that the 

 thin cover-glass (Cg) attached to its inner surface was opposite 

 to the pileus. Slipping of the plate was prevented by a horizontal 

 elastic band (HB) which passed around the back of the dish. 

 After the plate-cover had been applied to the dish, the gill to be 

 observed, shown on the right hand in Fig. 91, was about 2 mm. 

 from the surface of the cover-glass. 



The gill was observed with a horizontal microscope attached 

 to a stand of simple construction, an instrument which had already 

 been used to determine the rate of fall of spores (Fig. 92). 1 The 

 tube of the microscope was raised to the requisite height by 

 placing the stand on a wooden box, and was focussed by pushing 

 the stand backwards and forwards and by means of a brass 

 adjustment-screw. The tube-length was 130 mm. The ocular 

 was No. 4 and the objective No. 3 of the Leitz system. The 

 magnification was about 85 diameters and the field of vision 2 mm. 

 in diameter. The position and extent of the hymenial area, the 

 development of which was to be investigated with the microscope, 

 are shown by the dotted circle A, in Fig. 91. The illumination 

 of the hymenium was effected by light passing through the whole 

 substance of the gill. Diffused sunlight was employed during the 

 day and diffused electric light coming from strongly lighted white 

 paper at night. 



1 Cf. vol. i, 1909, p. 167, and Plate IV, Fig. 29. 



