STUDIES OF THE PINK BOLLWOBM IN MEXICO 55 
pressure and feeding, however, it was difficult to obtain a certain 
desired temperature in any one test, and the temperatures obtained 
in any series were usually very irregular. To this same irregularity 
in steam pressure and feeding can be ascribed the wide variations in 
temperature indicated in some of the individual samples. 
In the tests recorded in series 1, 2, 3, and 4 steam was admitted 
into the upper two conveyors of the machine only. The results in 
these four series show the maximum temperatures that failed to give 
100 per cent mortality for the respective periods of exposure to be as 
follows : 
Series 1, 1 minute, 5 seconds, 1423^2° F. 
Series 2, 55 seconds, 143° F. to 142° F. 
Series 3, 49 seconds, 152° F. to 148° F. 
Series 4, 47 seconds, 144° F. to 145° F. 
In series 5 steam was admitted into the two lower conveyors only 
and the seed required 1 minute and 8 seconds to pass through the 
machine. This would of course be equivalent to a machine with two 
conveyors only and an exposure of about 46 seconds. In series 6, 7, 
and 8 steam was admitted into the top conveyor only. The results 
in these series show the maximum temperatures that failed to give 
100 per cent to be as follows: 
Series 5, 1 minute, 8 seconds (46 sec), 160° F. 
Series 6, 1 minute, 8 seconds (all 100 per cent). 
Series 7, 55 seconds, 140° F. to 138° F. 
Series 8, 47 seconds, 143° F. to 145° F. 
These eight series throw considerable light upon the action of a 
machine of this type. In series 1 and series 5 the time of exposure is 
the same, or practically the same, and in each steam is admitted into 
two sections of conveyor. Under equal pressure this should heat the 
seed equally. Yet series 5 shows a failure at 160° F., and in series 1 
142 J^° is the maximum that did not give 100 per cent mortality, 
and it is a doubtful record. Other tests in series 5 compare with 
those in series 1 in a similar way. This brings out the point already 
mentioned, that the record obtained immediately after exposure does 
not show the temperature attained by the inside of individual seeds. 
From this it may be concluded that, in the test in series 5, enough 
steam had been injected into the seed mass to raise the seed to a 
temperature sufficient to kill the pink bollworm, were it bulked 
long enough to allow even heating throughout the mass by absorp- 
tion. This at the same time explains the better results obtained 
when steam was admitted into the upper conveyors only, giving 
opportunity for absorption of heat while the seed was passing 
through the lower dry conveyors. 
The results obtained in these tests warrant the conclusion that a 
machine of this type will be successful if operated so that the seed 
is discharged at a temperature of not less than 145° F. after an 
exposure of at least one minute, during the first half of which it is 
subjected to steam, the remaining time being allowed for penetra- 
tion of the heat to the larva inside the seed. The temperature 
record should be obtained at a point near the discharge end of the 
machine. 
EFFECT OF LIVE-STEAM TREATMENT ON GERMINATION 
A number of germination tests with samples taken from the series 
of tests just discussed were made. The results are given in Table 45. 
