i68 RESEARCHES ON FUNGI 



(Fig. 59), while above and below them there was a further space 

 of 0*5 mm. The magnification, namely, about 25 diameters, was 

 obtained by using a No. 1 Leitz objective and extending the draw- 

 tube. 



On viewing a field just below the gills, spores can be seen as 

 distinct but only just visible, very minute, dark objects, steadily 

 crossing the field in a vertical direction, apparently from below 

 upwards. Every spore so falling is not in focus, but, when the fungus 

 material is in good condition, spores in focus come into view at least 



^, i every five seconds. Often one can see 



three, four, or five spores in focus at the 

 Is same time. 



The spores fall vertically downwards 

 (apparently upwards). In the small cham- 

 ber employed, convection currents are re- 

 duced to a minimum and produce no 

 FIG. 59. The field of the 

 horizontal microscope, apparent disturbing effects on one s obser- 



apart ^ThT^ppCT^nd vations. Doubtless, there are very slow 

 lower horizontal threads a i r . currents i n the chamber, but I have 



in the eye-piece when 



seen in the field of view no reason to suppose in my critical experi- 



was 4-55 mm. . . 



ments with the large spores of Amamtopsis 



that they produced an error in the record of speeds of 2 per cent. 

 Even with the small spores of Collybia dryophila, which often 

 take eleven seconds to cross the field, the direction of the paths 

 of fall is vertical and there is practically no swerving from the 

 course. 



The records of the velocity of fall of the spores whilst crossing 

 the field of the horizontal microscope were made with the aid of 

 a large drum, which was driven by electricity and provided 

 with a delicate regulator (Plate IV., Fig. 29). A recording 

 fountain-pen produced a continuous spiral line upon the paper 

 as the drum rotated. To the pen was attached an electric 

 tapping key, which could be placed in a convenient situation 

 near the microscope. When the knob of the contact apparatus 

 was depressed, the pen immediately deviated from its course upon 

 the paper. 



When the apparatus was ready, the drum was set going and the 



