998 JOURXAL OF FORESTRY 



as contrasted with 51 per cent loss where the circulation was good 

 (humidity 12 per cent). While the humidity caused part of this dif- 

 ference, the effect of air circulation also seems clear. 



The whole matter of drying is made more compHcated by the inter- 

 relation there is between temperature, humidity, and air circulation. 

 An increase in temperature causes a lowering of the relative humidity 

 and ordinarily an increase in the rate of circulation. An increase in 

 circulation usually carries away surplus moisture, causing a decrease 

 in humidity, and often causes likewise a decrease in temperature. 



(d) Conditions in cone drying which affect the germination of seed. — 

 One lot of cones was dried for 10 hours, with 130° F. average tem- 

 perature, 56 per cent relative humidity, and poor air circulation. An- 

 other was similarly treated, except that the humidity averaged only 16 

 per cent. In the first case the germination was zero and in the second 

 case 6 per cent for seed extracted after kiln drying and 28 per cent for 

 seed which was protected by closed scales during the time in the kiln 

 and subsequently extracted by air drying. The 28 per cent is directly 

 comparable with the zero figures, for the treatment with high humidity 

 opened none of the cones and the seed was therefore later obtained by 

 air dry^ing. It is evident : ( i ) That high humidity with fairly high 

 temperature may kill seed, even though they be protected by closed 

 scales, and (2) that low humidity with fairly high temperature may 

 seriously injure seed exposed by the opening of scales without ma- 

 terially affecting seed protected by closed scales. 



The explanation of these results is of interest. The temperature of 

 the kiln is from some standpoints a matter of minor importance. A 

 main consideration is whether the seed themselves become dangerously 

 heated in drying. This depends largely upon whether the heat is con- 

 ducted readily to them and in turn upon the abundance of moisture, 

 which is a very much better conductor than air itself. Therefore if a 

 cone is wet, or if the relative humidity of the air is high, an air tem- 

 perature which otherwise would be harmless to seed may prove ex- 

 ceedingly dangerous. 



The seed protected by the closed scales in the treatment where the 

 humidity was low were evidently uninjured by the high temperature, 

 proving that heat was not conducted to them in dangerous degree. 

 The seeds not so protected were seriously damaged, but it appears not 

 through superheating. It seems rather that too much moisture was 

 evaporated from the seed, and that drying instead of heating was the 

 direct cause of loss. The exposed seed was 10 per cent lighter than the 

 protected seed, and though this seems a small difference it is reason- 



