1000 JOURNAL OP FORESTRY 



gradual increase of heat was advisable. As it worked out, the germina- 

 tion was variable, but averaged exactly the same (26^ per cent) in 

 each case. It therefore seems that it was not worth while to employ 

 gradually rising temperatures under the conditions of the tests. Nev- 

 ertheless it appears probable that with higher average temperatures, 

 and especially with fairly moist cones at higher temperatures, it would 

 pay to start with a low heat. This seems true, because it is now clear 

 that high temperature is particularly dangerous when moisture is abun- 

 dant, which is at the beginning of a run in most cases. The fact that 

 120° F. at the end of the rising temperature tests did not affect the 

 germination more than 100° F. did in the uniform temperature tests is 

 further proof along the same line. 



(g) Conclusions regarding cone drying: 



1. Cones must lose at least 35 per cent of their green weight to open 

 at all well. Almost all cones open when 40 per cent to 48 per cent, and 

 all when over 50 per cent is evaporated (unless the scales are under 

 pressure in drying, when they may never completely open). 



2. If seed cannot be extracted during drying, it is unwise to prolong 

 the drying indefinitely. As a rule, not over 40 per cent of the green- 

 cone weight should be evaporated, for the seed itself dries out danger- 

 ously beyond this point. This may often mean wasting some cones, 

 which do not open readily. 



3. Drying is the complex result of temperature, humidity, and air 

 circulation. 



4. A relatively low temperature (even 130° F.) may be fatal to seed 

 if the cones are green or the atmospheric humidity high. In this event 

 the heat is too readily conducted to the seed. 



5. A relatively low temperature (even 130° F.) may be dangerous 

 if any of the seed happens to be much exposed during treatment, and 

 especially so if the humidity is low. Here the effect would be excessive 

 drying, and even a loss of 10 per cent of the weight of the seeds may 

 be enough to be highly injurious. 



6. With green cones, which are not well adapted to kiln treatment, a 

 uniform temperature of over 100° F. is apt to cause great loss, largely 

 through the superheating of the seed. 



7. Cones moderately dry can be exposed to much higher tempera- 

 tures. Perhaps 140° F. is perfectly satisfactory. Nevertheless the 

 temperature should be as low as is compatible with economy, for great 

 heat always introduces the danger of excessive drying, even if it does 

 not involve the superheating, which is most common when moisture is 

 abundant. 



8. Rising temperatures appear to have much to commend them if 

 high temperatures are to be used and little to commend them in the 

 reverse case. This subject, however, has not been sufficiently investi- 

 gated. 



