■^nO JOURNAI. OF FORKSTRY 



in fact, both drought resistance and drought recovery are in the same 

 order as the rate of growth shown in the graphs, figures 3 and 4. 



Germination and Damping-off. — A prehminary experiment on the 

 relation of moisture to germination in raw humus throws an interesting 

 hght on the effect of dryness upon the rate of germination and upon 

 damp-ofif; for undecomposed raw humus is not the universally moist 

 substratum it is commonly supposed to be. In spite of its high mois- 

 ture-holding capacity, it is very porous and dries out rather rapidly. 

 Hence dryness is an important factor in reproduction, even in humid 

 regions. 



Red-pine seed was sown in pots containing raw humus of different 

 degrees of moisture. Pot i was watered daily ; pots 2 and 3 received 

 only rain water, which at the time of the experiment was not abundant 

 except for the first 18 days after sowing. Since the pots received full 

 sunlight for about three to four hours every day (as in many medium- 

 sized openings in the forest), the unwatered pots became rather dry 

 after only one or two days without rain. Pot 3 was drier than pot 2 

 because, instead of containing solid raw humus, it had only 3 to 4 

 centimeters of raw humus underdrained with 8 centimeters of rocky 

 soil. The effect of moisture upon the rate of germination was striking. 

 In the moist humus germination was rapid and uniform, 66 per cent 

 coming up within 5 days after the first appearance, while in the drier 

 pots germination was slow and straggling, 31 per cent coming up on 

 pot 2 and only 11 per cent on pot 3 in five days after the first appear- 

 ance. The seedlings in the moist humus were noticeably thriftier than 

 in the drier humus. 



The most unexpected result was the effect of dryness upon damping- 

 off. On nursery soils excessive moisture has generally increased the 

 damage from damping-off, while sunlight and dryness have been con- 

 sidered as preventives. In this case moisture prevented damping-off, 

 while dryness markedly increased it. On the moist humus the loss 

 from damping-off was nil ; on pot 2 the loss was 38 per cent and on 

 pot 3 it was 40 per cent of the number germinating. The explanation 

 is probably to be found in the great abundance of fungus spores in raw 

 humus and in the much greater vigor and power of resistance on the 

 part of the seedlings in the moist humus. It is also possible that the 

 high degree of moisture maintained a certain amount of acid continually 

 in solution in the humus, and that this acid retarded or prevented the 

 germination of the damping-off spores without affecting the seedlings. 

 It is well known that acid tends to prevent damping-off, and that one 

 of the most effective methods of combating the disease is treatment 



