RESULTS OF A STUDY OF DOUGLAS-FIR SEED 999 



able to suppose that it might have vast effect, since the moisture in no 

 case forms a great proportion of its weight. The theory of drying as 

 the cause of loss received support from the discussion under (b), where 

 it was shown that excessive drying of the cones went hand in hand 

 with reduced germination. 



A temperature of 130° F. has never been considered high for a kiln, 

 yet even it was injurious in the tests made. The difficulties with it may 

 be summarized as follows : 



1. With moist cones or air, the heat may be conducted to the seed so 

 readily that it becomes superheated. 



2. With dry cones or air, much of the seed may become dangerously 

 dry in kiln treatment, even before the majority of the cones open. 



(e) Best temperature for cone drying in a kiln. — The average figures 

 of Table 4 show the following germination, as correlated to the tem- 

 peratures used : 



140° F., one-half per cent germination. 

 130° F., 6 per cent germination. 

 120° F., 8 per cent germination. 

 100° F., 26y2 per cent germination. 

 80° F., 323/^ per cent germination. 



These results are very striking, as indicating the inadvisability of 

 using temperatures at all high if the cones are green. In general, the 

 seed must have been superheated through the rapid conduction of heat 

 by the moisture present. In some cases, however, excessive drying is 

 doubtless the direct cause of loss. It appears that green cones are not 

 well adapted to kiln treatment. 



These results can be applied only to green cones. Test 23 (not given 

 in Table 4) dealt with moderately dry cones, and with these the tem- 

 perature averaged 150° F., and for a few minutes reached 200° F., and 

 the relative humidity averaged about 22 per cent. Nevertheless the 

 germination was 10 per cent, which was better than the average for 

 120° F. There seems nothing improbable, therefore, in 140° F. being 

 suitable for cones moderately dry. Nevertheless it is believed best to 

 use a temperature as low as is compatible with economy, for a high 

 temperature always introduces the danger of excessive drying of seed, 

 even if it does not involve superheating. 



(/) Rising temperatures as compared with uniform ones. — Two tests 

 were made with temperatures rising gradually from 73° F. and 80° F. 

 to 120° F. The purpose was to compare these with runs having uni- 

 form average temperatures of 100° F., and determine whether the 



