23 



the flora of the right bank of the Ural between Uralsk and 

 Orsk differs in many ways from the flora of the left bank. 

 On the right bank we find for instance frequently: Arabis 

 pendala, Adenophora liliifolia, Tilia parvifolia, Primus Cha- 

 maecerasus, some Verbascum species, Urtica dioica and U. 

 urens, Senecio vulgaris and many others, but they disap- 

 pear totally on the left bank of the river and never appeal- 

 again 1 ). The unique character of the flora is still more 

 strongly expressed in the heart of the country, south 

 of 49 o N. Lat. Plant-forms such as Saxaul (Haloxylon Am- 

 modendron) Kara-Djusgjon (Ca/%omzm-species), the unfa- 

 miliar poplars Populus diversifolia and P. pruinosa, Kujan- 

 Sujok (Ammodendron Sieversii, A. Karelini) and the species 

 of Chenopodiaceae, Papilionaceae, Cruciferae &c. are all 

 unique in appearance and structure, and could only be 

 developed under special conditions of climate and soil. 

 In the Aralo-Caspian lands, the soil in particular has such 

 a great influence on the vegetation that a change of soil 

 - other conditions remaining the same often alters the 

 physiognomy totally and almost abruptly without any gra- 

 dual transitions. This change is most evident in the mo- 

 ving sand deserts, where the depressions between the sand- 

 hills are mainly covered by salt- swamps or by a loose 

 clayey bottom permeated with salts. The vegetation on the 

 sand-hills is varied and highly characteristic, but its spe- 



a ) BORZSZCOW comments on this in more detail in another place ("Ueber 

 die Natur d. Aralo-Casp. Flachlandes", p. 272, Anm.): on approaching the 

 steppe, the tree-vegetation disappears, poplars, elms, limes, birchen, willows, 

 Prunus Chamaecerasus and P. Padus; instead of Salix fragilis and S. vimi- 

 nalis so common in the Ural we have here S. pallida and S. Wilhelmsiana 

 and "sogar die, im Ganzen, dem Grassteppen-Gebiete angehorigen Straucher: 

 Caragana frutescens, Spiraea crenata u. hypericifolia und Amygdalus nana 

 kommen sudlich von Ural nur gruppenweise und selten vor" Stipa pennata 

 is replaced by S. capillata and S. Lessingiana. A great many plants disap- 

 pear altogether (Delphinium, Arabis, Trifolium, Fragaria, Scabiosa, Senecio, 

 Urtica, Poa, Aira &c.) The Ural is a line of demarcation between the grass 

 and forest region on one side, and the "true steppe" on the other. 



The change in the soil and vegetation south of Tshagan and the 

 steppe-mountains was, however, previously pointed out by PALLAS (1776, 

 p. 310). 



