266 RESEARCHES ON FUNGI 



specific gravity, and terminal velocity of the spherical spores of Amanitopsis 

 vaginata. The rate of fall of the spores was found to be about 46 per cent, 

 greater than was expected. While, therefore, the observed speed has proved 

 to be of the same order of magnitude as the calculated, Stokes' Law has not 

 been confirmed in detail. Ko fully satisfactory reason for the discrepancy 

 between theory and observation has so far been found. 



Chapters XV. and XVI. — The rate of fall of hymenomycetous spores 

 ranges from 0"3 to 6'0 mm. per second. It varies with the size of the 

 spores, their specific gravity, and the progress of desiccation. The rela- 

 tively very small spores of Collybia dryopliila in very dry air was found to 

 fall at an average rate of 0*37 mm. per second, whilst the relatively very 

 large spores of Amanitopsis vaginata in a saturated chamber attained a 

 speed of 6*08 mm. per second. The spores of the Mushroom (Psalliota 

 campestris), shortly after they have left the pileus, fall at a speed of 

 approximately 1 mm. per second. 



Chapter XVI. — The spores fall most rapidly between gills, down tubes, 

 &c, immediately after liberation from the sterigmata. After emerging 

 from the fruit-bodies, they dry up within about one minute. The diminu- 

 tion of volume causes a considerable reduction in the rate of fall. 



Chapter XVII. — The importance of violent spore-discharge lies in the 

 fact that thereby the very adhesive spores are prevented from touching one 

 another or any part of the hymenium whilst escaping from the fruit-body. 

 Each spore is shot out more or less horizontally into the spaces between 

 the gills, in hymenial tubes, &c. The horizontal motion is very rapidly 

 brought to an end owing to the resistance of the air. In consequence of 

 this, and also of the attraction of gravitation, the spore describes a sharp 

 curve and then falls vertically downwards. 



The path of the spore between the gills, in tubes, &c, has been called 

 the sporabola, and is remarkable in that it appears to make a sudden bend 

 approximately through a right angle. When for any spore the terminal 

 vertical velocity and the maximum horizontal distance of discharge have 

 been determined, its sporabola becomes amenable to a satisfactory mathe- 

 matical treatment. It was observed that the spores of Amanitopsis vaginata 

 are shot outwards from the gills in a horizontal direction to a maximal 

 distance of 0"2 mm. It was calculated that they complete this movement 

 in approximately ? ^ second, and leave the sterigmata with an initial 

 horizontal velocity of approximately 40 cm. per second. The steady, ter- 

 minal, vertical velocity of about 0*5 cm. per second is attained by the time 

 a spore has fallen a distance equal to its own diameter, i.e. about 10 /;.. 



Chapter XVIII. — At the moment of discharge, or within a few seconds 



