I 82 



RESEARCHES ON FUNGI 



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



A final, terminal, and fairly uniform velocity Avas 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. ()o) 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- 

 markiible 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 



section of a long almost immediately after liberation from the 



chamber u.sed ior gterigmata whilst they are passing out from 



measuring the » j i ft 



rates of fall of the fruit-bodics between gills, down tubes, &c., 



spores at difforont i • r ^  ^ 



distances from the and that after they have drifted m the con- 

 a,^ glass :'«, ptece vcction currents of the outer air for about 

 of pileus. At s YiaU a minute, thev reach a steady terminal 



and t are shown  •' _ _ 



two fields as seen velocity considerably less than the initial, 



with the horizon- , ^ 



tal microscope (i We can only suppose' that at tlie moniciit or 



liberation the spores are fully turgid, and that 



cms. and 12 cms. 

 below the gills 



respectively. One- j^y l\^^. yjipiJ logs of water they become dried 



half actual size. . . 



up in less than a minute. Tt is certainly a 

 good arrangement that the spores should fall (.lown between the 

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

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



