THE RATE OF FALL OF SPORES 



171 



record of the spores on the drum could then be calculated. Since 

 this average time was that required for the spores to fall through 

 a distance of -t'SS mm., the average velocity of fall of the spores 

 could be calculated. 



The following figures give the drum records of 200 spores of 

 Amanitopsis vaginata} The first series of 100 took about twelve 

 minutes to record. After an interval of forty minutes, the second 

 series of 100 was made. The drum records, measured on the drum 

 by means of a steel tape, are given in centimetres. 



Average distance on drum in Series I. 

 = 0-8662 cm. 



Average speed of drum = 1-16 cm. per 

 second. 



Hence average time of fall of each 

 spore in falling through a field of 4-55 

 mm. = 0-747 seconds. 



Hence average velocity of fall = 



= 6-09 mm. per second. 



Average distance on drum in Series 

 II. =0-8719 cm. 



Average speed of drum = ri6 cm. per 

 second. 



Hence avei-age time of fall of each 



spore in falling through a field of 4-55 



mm. =0-752 seconds. 



4*55 

 Hence average velocity of fall = ^_ " 



= 6-05 mm. per second. 



Hence average velocity for both Series together = 6-07 mm. per second. 



^ Specimen I. in Chap. XIV. 



