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RESEARCHES ON FUNGI 



7 



indicates that the horizontal velocity is reduced to zero by the 

 time the spore has fallen through a distance only about equal 

 to its diameter. 



It must often happen that spores are not shot outwards in 

 exactly the horizontal direction but at a greater or less angle 

 thereto. The paths of spores projected with equal velocities 

 at various angles can be deduced mathematically, and are indi- 

 _^ cated diagrammatically in the ad- 

 joining figure (Fig. 65). That the 

 sporabola appears to consist of two 

 parts, one due to violent projection 

 of a spore and the other due to 

 gravitation, again becomes obvious. 

 We may conclude that, if a basidium 

 looks upwards, it will shoot its spores 

 to a height approximately equal to 

 the maximum horizontal distance to 

 which it would have projected them 

 if it had been placed horizontally 

 FIG 65.-Sporaboias of spores shot instead of vertically. Quite generally, 



outwards from a point at various * 



angles with the vertical and with the sudden bend in each sporabola 



equal initial velocities. . . -11 



takes place at approximately the same 



distance from the point of projection at the surface of a limiting 

 sphere (Fig. 65). 



Before attaining its steady terminal velocity, a spore requires to 

 fall but a very minute distance. This may be shown as follows : 



Let X = the maximum horizontal distance of projection, 



x = the distance of a point on the sporabola from the vertical axis, 

 V = the terminal vertical velocity, and 

 v = the vertical velocity at any time. 



Then it may be deduced that 



X _ V 



X~V 



By substituting the value of ^ in the equation for a sporabola 

 we get 



