A. N. KRASSNOF — THE RUSSIAN " BLACK EARTH." 71 



bands, the isokumic bands, encircling the region richest in humus, where the " black 

 earth " contains as much as l(i per cent of organic substances. 



These researches in European Russia attracted the attention of our geologists and 

 botanists, and soon it was learned that in the various parts of Asiatic Russia, where 

 the climatic conditions bear some resemblance to those of chernozem Russia, soils 

 had been found that were analogous if not identical with the "black earth" of 

 Dokuchaef. Thus in the Crimea, in the northern foothills of the Caucasus, in 

 Siberia, and lastly in Turkestan, on the northern slopes of the Thian Shan, " black 

 earth " was found varying in quality according to the climatic law of Dokuchaef. 

 Thus, too, the great Black-Caspian depression is nearly surrounded by a zone of 

 " black earth " varying in breadth and in richness according to the conditions of 

 heat and moisture, and accompanied by a nearly identical vegetation. 



The question of the causes of the geographic distribution of the " black earth " 

 being thus solved, did not yet supply an answer to the question, still more interest- 

 ing from a geologic point of view : the question of the age of the " black earth." 

 Unfortunately there exist but very few observations on this point. The chemical 

 analyses of the " black earth," taken in different parts of Russia, show that the 

 organic substances of the chernozem are accompanied by a number of peculiarities. 

 The quantity of hygroscopic water, of phosphates and of ceoliths, becomes larger in 

 proportion as the relative quantity of humus increases. As these properties are of 

 great agronomic value, the zemstvos (or assemblies) of some Russian governments 

 undertook special investigations of these soils. The zemstvos of Nizhni Novgorod 

 and Poltava prepared maps of their soils, under the supervision of Professor Doku- 

 chaef. The detailed investigations made in those provinces yielded very interest- 

 ing results, a part of which are summarized in the appended tabic They showed 

 that even in the same climate and on the same geologic formations the qualities of 

 the soils may be very different, and that the relief plays an important part in this 

 matter. Thus, for example, Professor Dokuchaef at Poltava, and myself at Khar- 

 kof, found the following relations to exist between soil, vegetation and relief: 



1. The highest points and those most cut up by crevasses and valleys are richest 

 in forests and in gray soils, and the number of forests increases in proportion to the 

 number of crevasses. On the contrary, the points of gentle, flat relief, sparely pro- 

 vided with deep cuts — in a word, poorly drained — are the region of the "black 

 earth" and of the steppe. 



2. The qualities of the "black earth " vary with relative height. The highest 

 points of the steppe are at the same time the richest in humus, although the differ- 

 ence in height is only one to three hundred feet. 



.'!. The regions of the gray soils, especially when they accompany the high banks 

 of streams, are skirted by a zone of intermediate soils formed of the " black earth" 

 half transformed into gray forest soil. 



4. The vegetation of the less elevated parts, though composed of species peculiar 

 to the steppe, is less rich in characteristic forms than those of the relatively more 

 elevated parts; while the latter, despite its steppe character, contains several water- 

 loving forms, the former is rich in endemic tonus or forms common to it and the 

 Caucasus and its Alpine and sub-Alpine regions. 



if we observe the relief of these provinces, we shall see very interesting phenomena. 

 Where the soils are covered by forest t hey overlie eit her ( Yetaceoiis rocky subsoils 

 or Quaternary clays, drained in all directions by gullies. Quite a different aspect 

 is presented by the level lands covered by the " black earth." There the ground is 



