38 RESEARCHES ON FUNGI 



nearly a right angle into a vertical position where further move- 

 ment was stopped by the arms and platform. The slamming- 

 board, which was 7 inches longer than the platform was high, was 

 thus caused to strike the projecting part of the balloon with con- 

 siderable violence. In response to the blow from the slamming- 

 board, the balloon shot forward into the air through a horizontal 

 distance of about 3 to 6 feet ; and it then made a sharp turn 

 downwards, thus completing its sporabolic trajectory. 



The gun was used to discharge both spherical and oval balloons 

 in a horizontal direction, and the results obtained with it did not 

 differ in any essential from the results obtained by casting the 

 balloons forward with the hand. The balloon shown in Fig. 13 was 

 1 inches long and slightly oval. When fired from the platform, it shot 

 forward to a distance of 6 feet before beginning to fall verticaUy. 



When an elongated balloon, 13 inches long and 6 inches wide, 

 was set on the discharging platform with its long axis in the direction 

 of the axis of the gun and of the line of flight and was then dis- 

 charged, it was observed that, during its flight, the balloon turned 

 through an angle of 90 so that its long axis, while remaining 

 horizontal, came to be turned in a direction which was transverse 

 to the line of flight. The same result was obtained by casting 

 elongated balloons forward by hand. This turning movement is 

 exactly what one should expect on the principle that a moving 

 body tends to present its greatest surface to the resistance of the 

 air. Theory and observation both permit one, therefore, to draw 

 the conclusion that an elongated spore, when shot from a sterigma 

 or out of an ascus and whilst moving against the resistance of the 

 air, must tend to turn its long axis from its original direction through 

 a right angle. 



A Comparison of the Rates of Fall of Spores and Thistle-down. 

 If the spores of Hymenomycetes, when suspended in the air on 

 an autumn day, were to have their diameters suddenly increased 

 100 times without this increase altering their normal rate of fall, 

 we should see them with the naked eye, and they would often 

 darken the air and astonish us with their vast numbers and extra- 

 ordinary variety. We should be most struck, perhaps, by the 

 slowness of their rate of fall. In particular, it would be necessary 



