6o2 ZONES AND REGIONS [Pt. Ill, Sect. II 



go at all beyond them. The large tracts of flat ground that lie between these river 

 valleys and ravines are entirely free from forest, and, being covered with the 

 characteristic steppe-vegetation, are most intimately associated with the true steppe 

 district. But further north again, where the forests begin to extend into the plain, 

 their areas are very small, and their proportion to the total area of the country 

 insignificant, the land being still always mainly dominated by herbaceous formations. 

 All forests along the entire boundary line are, almost without exception, pure oak- 

 forest : they are throughout formed of Quercus sessiliflora, sometimes Q. peduncu- 

 lata and Q. pubescens appear in small numbers ; very rarely does one find, and 

 then only on the border of the oak-forests, a mixture of Acer campestre, Ulmus 

 effusa, U. campestris, and Carpinus Betulus. In such oak-forest the indigenous shrubs 

 are very numerous and form a dense underwood, in which occasionally the pretty 

 Rosa altaica occurs. In the absence of this underwood, the soil is covered by 

 a great number of herbaceous plants forming a very luxuriant and diversified 

 meadow-like vegetation which is almost everywhere mown.' The accompanying 

 list of the chief constituents of these forest-meadows enumerates a number of 

 species which usually also occur in the forests of Central Europe and in grassy 

 clearings in the forest, especially on a calcareous subsoil. 



' Besides the oak, Carpinus Betulus is prominent on the border of the forest 

 district, so that oak-woods and hornbeam-woods exclusively form the forest 

 formations on the border of the steppe districts and forest districts. The hornbeam 

 sometimes appears isolated on the margin of the oak-forests, but otherwise it forms 

 independent woods, which have no connexion whatever with the oak-forests and 

 are distinguished from them most strikingly by their physiognomy. Whilst in 

 an oak-forest the trees are very scattered but are individual^ fine, the hornbeam- 

 woods are formed of very slender, thin and weakly individuals, which however 

 occur in enormous numbers and form an impenetrable dark thicket. In such 

 cases the hornbeam permits the intrusion of no other trees or shrubs, and the 

 rich underwood of the oak-forest is completely absent. Shrubs cannot thrive 

 here on account of the want of light, and the same cause also appears to exclude 

 all herbaceous plants.' 



SELECT LITERATURE. 



Drude, O. Deutschlands Pflanzengeographie. Bd. I, p. 339. 1896. 



Gruner, L. Zur Charakteristik der Boden- und Vegetationsverhaltnisse des Steppen- 



gebiets und der Dniepr- und Konka-Niederung unterhalb Alexandrowsk. 



Bullet, de la Societe imper. des natural, de Moscou. Annee 1872. No. 1. 

 Hackel, E. Ueber einige Eigenthiimlichkeiten der Graser trockener Klimate. 



Verhandl. der zoolog.-botan. Gesellsch. Wien. 1890. 

 Hitchcock, A. S. Oecological Plant Geography of Kansas. Transactions of the 



Academy of Science of St. Louis. Vol. VIII. 1898. 

 Krasnov, A. I. Geobotanical Researches in the Kalmuk Steppe. Bulletin of the 



Russian Geographical Society. Vol. XXII. 1886. (In Russian.) Extended 



reference by F. von Herder in Engler's Jahrbucher. Bd. X. 1889. Litteratur- 



bericht, p. 53. 



