THE RATE OF FALL OF SPORES 



167 



FIG. 



sealed in the disc-shaped chamber of which the base and top con- 

 sisted of glass. The compressor cell was then placed in the vertical 

 position (i.e. with the glass plates vertical) and clamped by one end 

 to a stand. By this means it was possible to cause the gills to look 

 vertically downwards in the natural manner. Thus enclosed in the 

 chamber, the gills continued to rain down spores for some hours. 



In order to observe the 

 falling spores, a special micro- 

 scope on a stand of simple 

 construction l was employed. 

 The microscope tube was placed 

 in the horizontal position 

 (Plate IV., Fig. 29), and could 

 be screwed upwards and down- 

 wards by means of a rackwork 

 on the stand. The amount of 

 rise or fall could be read off 

 on a vertical scale to which 

 a vernier was attached. The 

 microscope tube was arranged 

 at such a height and at such a 

 distance from the chamber as 

 to focus a field (shown by the 

 dotted ring in Fig. 58) immedi- 

 ately below the gills where the 

 spores were falling. To illu- 

 minate the microscope, diffuse 

 daylight, obtained from the 

 glass roof, was reflected into 

 the tube by means of a plane mirror (Plate IV., Fig. 29). The 

 observations were made in a basement room where the temperature 

 was very constant for considerable intervals of time. 



The horizontal microscope was provided with a Ramsden eye- 

 piece. Three fine silk threads were attached to it so as to cross the 

 field of view. The distance between the extreme threads, as seen in 

 the field of view when the microscope was focussed, was 4'55 mm. 

 1 Made by Pye & Co. 



58. The compressor cell used for 

 measuring the rate of fall of spores. A 

 section of the cell is shown above : the 

 chamber c can be varied in size by rais- 

 ing or pressing down the cap. g, glass. 

 Below is shown the cell when in use. ;<, 

 a piece of pileus with gills looking down- 

 wards (c/. Fig. 57); 6, b, wet blotting- 

 paper or cotton-wool; w, a free drop of 

 water. The dotted circle shows the field 

 of view of the horizontal microscope when 

 focussed just beneath the gills. The 

 three arrows show the courses of three 

 spores falling from between the gills and 

 crossing the field. The horizontal lines 

 in the latter are produced by three silk 

 threads in the Ramsden eye- piece. Actual 

 size. 



