328 Forestry Quarterly 



finally if artificially dried, they lose almost entirely their water- 

 absorbing quality. 



The time element, then, must be taken into consideration. But 

 since in nature constantly additions of water by rain and humidity 

 are replenished, so that new colloids can be formed, they never 

 attain this condition. 



It is proved that raw humus reacts acid and that moss-turf con- 

 tains acid which, however, do not form salts ; also that humus 

 material react partly neutral, partly alkaline, partly acid, but lack 

 some characteristics of acids, hence true acids are probably not 

 present, but presumably colloids. According to colloid contents, 

 soils are more or less stable, the soils deficient in colloids having 

 the tendency to slide. 



The presence and quantity of colloids can be tested by the ease 

 of absorption and aniline colors, so that it is easy to determine 

 for practical purposes the value of the soil. 



The author, then, refers the low water stages in German rivers 

 to lack of colloids. The widespread change of broadleaf by coni- 

 ferous woods has the consequence of reducing the humus cover, 

 and hence the capacity for absorption of water and vapor has 

 been reduced. 



Especially with regard to waste lands this lack of colloids is 

 important and must be supplied by adding clayey or humus 

 material. 



In connection with the discussion on the colloids of peat, the 

 interesting statement is made, that during the war there has 

 been developed a method of substituting peat for cork. Peat 

 of moss, heather, roots of alder and willow can be compressed into 

 plates of varying thickness and hardness and serve satisfactorily 

 as protection against heat and cold in hospitals and barracks. 



Die Bedeutung der BodenkoUoide fiir die Forsl- und Landwirlhschaft. Forst- 

 wissenschaftliches Centralblatt, 1915, pp. 2.57-63, 455-60. 



Since earthworms are supposed to be nse- 



Food ful in comminuting the soil, it is of interest 



of to note that, according to von Aichberger's 



Earthworms careful studies, the earthworm feeds mainly 



on the edaphon, i. e., minute animals of the 



lowest orders, of which 1 cubic millimeter may contain as many 



