140 RESEARCHES ON FUNGI 



It is now clear to me that the apparent shooting out of spores 

 from the vertically-placed hymenium in the many Agaricinese and 

 Polyporese observed by my first method is simply an illusion. 

 During the apparent bombardment of hundreds of spores into a 

 cross section of a tube of Polyporus squamosus, or into the spaces 

 between two gills in a Mushroom (which one sees in looking down 

 upon such sections as those represented in Figs. 47 and 48), one 

 does not really see a single spore performing any part of its 

 horizontal motion. The spores are falling vertically as soon as 

 ever perceived. By methods to be described in Chapter XVII. it 

 has been found that for Amanitopsis vaginata the total horizontal 

 distance to which the spores are projected, namely, about 0'2 mm., 

 is accomplished in approximately only 4^ second, and that the 

 initial velocity with which each spore is shot forward is about 

 400 mm. per second. From a consideration of these remarkable 

 figures, and also the fact that the spores must be considerably 

 magnified in order to be seen at all, it seems to me very improbable 

 that the human eye, aided as it must be by the microscope, will 

 ever be able to detect the horizontal motion of a spore. Whether 

 or not it is possible to do so must be left to the experimental 

 psychologist. That the downward motion of a spore, which is 

 performed at a constant speed in response to gravity, should be 

 observed as described is easily understood, for it is performed 

 relatively much more slowly and for a much longer distance than 

 the horizontal motion. In the case of Amanitopsis vaginata the 

 terminal vertical velocity is only about 5 mm. per second. In 

 most other species, where the spores are smaller, the velocity is 

 usually only 1-2 mm. per second. 1 These theoretical considera- 

 tions, which it has been necessary to introduce in this place in 

 order to explain the results of observations Avith Method I., will 

 doubtless become clearer to the reader when the curious nature 

 of the "sporabola" has been discussed in a subsequent chapter. 



Observations, with the special object of seeing the horizontal 



flight of particular spores on leaving the sterigtnata, were made 



with sections of Polyporus squamosus like that in Fig. 47 on several 



occasions, but they gave only negative results. With a vertical 



1 Vide infra, Chaps. XV. and XVI. 



