CHAPTER XVII 



THE PATH OF THE SPORES BETWEEN THE GILLS, ETC. THE 

 SPORABOLA- APPENDIX ON THE MOTION OF A SPHERE IN A 

 VISCOUS MEDIUM 



BY methods already explained, it has been shown that it is possible 

 to determine by observation (1) the maximum horizontal distance 

 to which a spore travels when it has been shot out horizontally 

 from a basidium lying in the hymenium of a gill, 1 and (2) the 

 terminal vertical velocity with which the spore falls toward the 

 earth. 2 With a knowledge of these data, and assuming that the 

 resistance of the air is proportional to the velocity, it is possible 

 to calculate the initial velocity with which a spore is shot off its 

 sterigma, and also to map out the trajectory described. 



The initial velocity with which a spore leaves its sterigma, 

 when projected in a horizontal direction, may be calculated as 

 follows : 



Let V=the terminal vertical velocity, 



X = the maximum horizontal distance of projection, 

 H the initial horizontal velocity, and 

 <jr = the acceleration due to gravity. 



It can be shown 3 that 



For spores of Amanitopsis vaginata, it has been observed that 

 X = 0'02 cm. and V = 0*5 cm. per second approximately, whence 



H = 981xO-02 

 0-5 



i.e. the spores are projected in the horizontal direction from the 

 sterigmata with an initial velocity of approximately 40 cm. per 



1 Method II., Chap. XI. a Chap. XV. 



3 A note on the motion of a sphere in a viscous medium is given in the 

 Appendix to this chapter for convenience of reference. 



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