I40 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



21. Continental Notes — France. 



By A. G. Hobart-IIampden. 



I. — One might think that the apparent awakening of the soil, 

 and the germination of seeds, at the end of winter was merely 

 due to the increase of temperature, but M. Auguste Lumi^re 

 shows, in the Comptes Retidus of the French Academy of 

 Sciences, that germination can be brought about, even in 

 winter, without change of temperature by washing the soil 

 with sterilised water, thus removing substances which prevent 

 germination. He attributes great importance, in regard to this 

 phenomenon of the sterility of the soil, to the action of the 

 products of disintegration coming from the dead leaves and the 

 debris of annual plants, and also substances rejected by roots. 

 These products of disintegration contain reducing bodies {corps 

 reducteurs) which oppose all germination. Germination needs 

 intense oxidation, and the dead leaves, etc., absorb the avail- 

 able oxygen, while the soil remains sterile until the atmospheric 

 oxygen, having penetrated, either directly or in rain, has 

 completely oxidised the reducing substances. This explains 

 the utility of digging, which brings to the surface the lower 

 layers of the soil, which are impregnated with these sterilising 

 agents, and thus completely paralyses them. This would be 

 the scientific explanation of the difficulty experienced by the 

 silver fir in establishing itself in a beech wood, or by the spruce 

 in regenerating itself on its own needle-covered soil. Thus it 

 is important, we are told, not to replant immediately the area 

 of clear-felled conifer woods — to wait two, three, or four years 

 is not a loss of time. This is not quite the same thing as in 

 the case of sowing, when much oxygen is required for germina- 

 tion, but in practice things appear to work out in the same 

 way with planting. The remark may be offered that possibly 

 the burning of the soil surface when this is feasible, previous 

 to sowing (or even perhaps planting) would help a great deal. 

 As to the effect of digging, the writer of these Notes can quote 

 a remarkable example. Many years ago he tried the experiment 

 of digging an irregular patch, in the Bhinga Forest in Oudh, 

 below some Sal {Shored) seed-bearers, just at the break of the 

 rains, when the Sal seed falls. The result was a profuse crop 

 of seedlings just where the digging had been done, while 



