RESEARCHES ON FUNGI 



second 1 and third contacts were made as the spore crossed the 



second and the third lines 

 respectively. Thus for 

 the fall of each spore the 

 pen deviated three times 

 from its normal path on 

 the paper of the drum 

 (Figs. 60 and 61). The 

 fall of about 100 spores 

 was recorded in this way 

 as rapidly as possible, the 

 entire record usually be- 

 ing completed in less than 

 fifteen minutes. A time 

 record of ten seconds was 

 always made on the drum 

 before and after each 

 series of observations by 

 means of a chronometer 

 ticking half-seconds. The 

 drum kept up a very con- 

 stant peripheral velocity, 

 which was usually T16 

 cm. per second. When the 

 records had been made, 

 they were measured off 

 on the drum by means of 

 a steel tape, added up, and 

 the average taken. By 

 measuring the distance 

 run by the drum in ten seconds, the speed of the drum could be 

 determined. The average length of time represented by the average 



1 There was no absolute necessity to record the passing of the middle line by 

 a spore, but it was found convenient to do so for the purpose of distinguishing 

 the individual spore-records from one another on the drum. Every effort was 

 made to make the first and third contacts precisely at the times the upper and 

 lower lines were being crossed ; but the second contact, being of quite secondary 

 importance, was naturally not always recorded so accurately. The middle line 

 was 2'22 mm. from the upper line and 2'33 mm. from the lower line. 



