I 82 



RESEARCHES ON FUNGI 



continue in a more or less marked manner for about 10 cm. 



A final, terminal, and fairly uniform velocity was then reached, 

 the time required for its attainment being less 

 than half a minute after the spores had been 

 liberated from the gills. The following curves 

 (Fig. 63) give the results of the observations. 

 Each velocity plotted is the average of about 

 twenty-five velocities recorded in sequence. 



The curve for the Mushroom spores is re- 

 markable in that it first of all sinks and then 

 rises again. Possibly this is accounted for on 

 the supposition that the spores buckle up 

 after a certain stage of desiccation has been 

 reached. Such a mode of contraction would 

 decrease the surface exposed in falling, and 

 thus increase the velocity. As a matter of 

 fact, Mushroom spores, when drying on a glass 

 slide, rapidly become indented on one side so 

 that they more or less assume the form of a 

 boat. 



A general conclusion which may be arrived 

 at from the data contained in this chapter 

 is, that in nature spores fall most rapidly 

 almost immediately after liberation from the 

 sterigmata whilst they are passing out from 

 the fruit-bodies between gills, down tubes, &c, 

 and that after they have drifted in the con- 

 vection currents of the outer air for about 

 half a minute, they reach a steady terminal 

 velocity considerably less than the initial. 



with the horizon- 

 tal microscope o We can onty suppose that at the moment or 



below 11 the" 2-iiis liberation the spores are fully turgid, and that 

 respectively. One- Dy t } ie rap icJ loss of water they become dried 



half actual size. * l j 



up in less than a minute. It is certainly a 

 good arrangement that the spores should fall down between the 

 gills or in hymenial tubes, &c, Avith the greatest velocity, for 

 they thus escape from the fruit-bodies with the least risk of 



Fig. (12.— Plan and 

 section of a long 

 chamber used for 

 measuring the 

 rates of fall of 

 spores at different 

 distances from the 

 gills. b, brass ; 

 g, glass ; p, piece 

 of pileus. At s 

 and t are shown 

 two fields as seen 



