The Black Earth. 311 



the roots of trees, at the same tirae possessing considerable powers 

 of resistance to pressure, that is, failing to crumble readily when, 

 rubbed between the fingers. 



Researches in the Nijui Novgorod and Poltava governments prove 

 that a hundred years after the cutting down of the forests the soil 

 still preserves its original character. If woods be not the source 

 of the rich deposit, the present character of the steppe areas may 

 serve to furnish a solution to the problem. There are still some 

 districts not yet touched by the agriculturist, where the virgin soil 

 produces a rank vegetation, luxuriant or sparse according to the 

 amount of rainfall, A notable growth is a peculiarly wiry grass, 

 that blunts the edge of the sharpest scythe. On the great plains 

 E. of the Dnieper, in the region not devoted to the cultivation of 

 cereals, Euphorbiaceous plants and Compositee largely predominate. 

 Indeed, so favourable is the soil for the growth of the latter, that 

 one of the lihAsilQ^, Xantliium spinosum, (introduced some thirty years 

 ago with the Bohemian settlers) has become a widespreading pest, 

 and threatens even to supplant the indigenous flora. 



In travelling over these plains, I early came to the conclusion that 

 the decomposition of these plant-remains, and the intimate inter- 

 mixtui'e of a poi'tion of their protoplasmic contents with the particles 

 of the Loess soil, were the true causes of the formation of Black 

 Earth. In the autumn the dried stems which roll over the steppe, 

 often bound together in large bundles, bear witness to the large 

 amount of plant-waste which must then go on. At the same time 

 the roots remain in the soil, giving rise to great matted fibrous layers 

 which prevent the penetration of water to the lower levels. Indeed, 

 there are circumstances in which such roots may attain the thickness 

 of a man's thumb. Many of them will probably undergo decom- 

 position, but, thanks to the fine-grained character of the soil, 

 the materials necessary for the production of the humus would be 

 concentrated rather than diffused through it. 



Von Richthofen {loc. cit. p. 300) remarks: "The Black Earth of 

 Southern Russia is growing (owing to dust transported by wind 

 action). The black colour, which is proper to the uppermost layer 

 only, appears to result solelj'^ from the formation of vegetable mould, 

 the deeper portions showing the brown colour of the Loess, together 

 with its structure, although this appears to be less perfect than in 

 the former case." 



Prof. Lewakowsky, of Kharkov University, has approached this 

 interesting subject from the chemical point of view. He finds that 

 the organic matters form, at a shallow depth, definite chemical 

 combinations with the soil constituents, alumina, iron oxides, and 

 calcium compounds. These compounds are exposed to the oxydizing 

 action of the air, becoming gradually of darker tints, till eventually 

 they form the Tchernozem itself. He explains the absence of Black 

 Earth in forest regions as follows : The soluble organic materials 

 which are prevented from passing into the soil, owing to the thick 

 deposit of fallen leaves, undergo changes under the influence of the 

 atmosphere, and become insoluble or even burnt by its oxydizing 



