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RESEARCHES ON FUNGI 



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 tigure (Fig. Go). 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.— Sporabolas of spores shot instead of vertically. Quite generally, 



outwards from a point at various ./^ ^ o j 



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



equal initial velocities. , , . 



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, 



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

 V = the terminal vertical velocity, and 

 ?; = the vertical velocity at any time. 



Then it may be deduced that 



X V 



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

 we get 



