34 RESEARCHES ON FUNGI 



which I called a sporabola, is remarkable in that roughly it can be 

 divided into two parts a part due to the projection of the spore 

 and a part due to the fall of the spore towards the ground. A spore, 

 shot out horizontally from a gill, goes forward for about 0-1 mm. 

 and then makes a sharp turn through a right angle, after which 

 it falls under gravity vertically downwards with a constant terminal 

 velocity. 



To demonstrate the nature of this peculiar trajectory on a 

 large scale, I have invented the balloon-gun which has been so 

 named because its projectiles are balloons. In the development of 

 certain guns used in the Great War, the object has been to throw 

 a projectile of large volume and high density a distance of several 

 miles. In developing my balloon-gun, on the other hand, the object 

 has been to throw a projectile of large volume but very small 

 density (i.e. just exceeding that of air) a distance of a few feet only. 

 Thus, while the size of my projectiles has not greatly differed from 

 the size of the shells of large field guns, the density has been very 

 much smaller. My projectiles, it must be admitted, although of 

 considerable scientific interest, appear somewhat ridiculous to those 

 who see them in action for the first time, but they have this ad- 

 vantage over the shells of the battlefield : their motions provoke 

 laughter rather than tears. 



The balloons which I have used as projectiles have been spherical 

 and oval toy-balloons which, when inflated, resemble in form the 

 two chief types of basidiospores. Their size was varied by choosing 

 larger or smaller envelopes and by altering the amount of gas with 

 which any one balloon was inflated. The spherical balloons were 

 mostly about 6 inches in diameter and the oval ones 10-24 inches 

 long and 6 inches wide. The gas pressed into a balloon was either 

 air or a mixture of air and coal-gas. The mixture, of course, is 

 lighter than air ; and, by filling a balloon with a mixture in which 

 the components were suitably balanced, the rate of fall of the 

 balloon could be reduced to whatever was desired. However, most 

 of my experiments were carried out with balloons filled with air. 



A toy-balloon which falls very slowly in air resembles a spore 

 in that it has an enormous volume and surface area relatively 

 to its mass. Therefore, not only in having a spherical or oval 



