THE RATE OF FALL OF SPORES 



16= 



holds for the fall of small spheres in air appears to be that obtained 

 by J. J. Thomson, whose value of the electronic charge, obtained 

 by Wilson's^ cloud method involving the assumption of Stokes' 

 Law, was found to agree with the generally accepted value of the 

 electronic charge as calculated by application of the kinetic theory 



B 



Fig. 5(). — Amanitopsis vaginata. Relations of the spores to the fruit-body. A, 

 transverse section through two gills showing the hymenium, h, from which 

 basidia are projecting. The arrows indicate the paths of spores which, after 

 discharge from their basidia, have fallen in still air. Magnification, 15. B, 

 vertical section through the hymenium and subhymenium. p, paraphyses : 

 a-c, basidia ; a, with rudimentary spores ; b, with ripe spores ; c, with two 

 spores discharged ; d, with three spores discharged ; c. with all the spores 

 discharged : s, the subhymenium. Magnification, 370. C, isolated basidium 

 with two spores discharged showing mode of attachment of spores to their 

 sterigmata. Magnification, 1110. D, discharged spore. Magnification, 

 1110. E, basidium with rudimentary spores. Magnification, 1110. 



of gases. This verification of the applicability of Stokes' LaAv is, 

 of course, very indirect. 



It seemed to me of interest to attempt to determine experi- 

 mentally whether the spores of Hymenomycetes fall in accordance 

 with Stokes' Law. It Avas hoped that, by making three separate 

 measurements of the specific gravity, size, and velocity of fall of 



1 C. T. R. Wilson, Phil. Trans., 1897. 



