20 Floristik, Geographie, Systematik etc. 



Paulsen, O., Studies on the Vegetation of the Transcas- 

 pian Lowlands. (The second Danish Pamir expedition conduc- 

 ted by O. Olufsen). 279 pp. 79 figs. and a map. Copenhagen 1912. 



The subject of this contribution is the piain east of the Cas- 

 pian Sea, its eastern limit is the Kara Tau Mountains, and 

 towards the north the boundary is fixed at 46° N. Lat. It is a part of 

 what Musketow terms Asia-Media, but according to Richtho- 

 fe n's terminology it belongs to the peripheral region. In the earlier 

 part of the book features of the geology of the land are given (with 

 Chemical analyses of salts), and the general aspects of the climate 

 are described. In a foUowing chapter earlier litterature concerning 

 the Vegetation is abstracted, special stress being laid upon Russian 

 papers, almost unknown in western Europe. In chapter 5 the for- 

 mations are classified in Grisebach's sense; they are the foUowing: 



1. Salt-desert, 2. Clay-desert, 3. Stone-desert, 4. Sand-desert, 5. 

 Riverside Thickets. It is emphasized that none of these formations 

 is to be regarded as Steppe, which term must be reserved exclusi- 

 vely for grasssteppe. This latter is defined as mainly a closed plant- 

 formation (or group of formations) occurring on soil rieh in humus 

 without excess of sulphates and Chlorids, and with a comparatively 

 moist surface-soil; the Vegetation consists of herbaceous perennials, 

 undershrubs and annuals while trees and bushes are wanting. The 

 soil of the desert, on the contrary, is devoid of humus or very poor 

 in humus, and contains many sulphates and Chlorides. The subsoil 

 is (always?) better supplied with water than the surface. The for- 

 mations are very open and they frequently include trees and bushes. 



In the foUowing chapters the formations are described as to 

 their appearance, occurring species, different facies and aspects, 

 They are provisionally distinguished from each other by their soils. 

 The Salt-desert has mostly clay, always covered by salts; the Vege- 

 tation is very scattered consisting of annual or perennial Halophy- 

 tes, of which all are summer-plants. The soil in the Clay-desert is 

 mostly Loess. Here, an early aspect of ephemeral spring-plants is 

 found, consisting of numerous species, mostly annuals, but there is 

 also a certain number of perennials with shortliving aerial shoots. 

 The spring-plants are mostly low and have no pronounced xero- 

 phytic structure. The summer-plants are scattered and have a 

 marked xerophytic structure; they include small shrubs and under- 

 shrubs, perennials and long-lived annuals. 



The Stone-deserts are mainly characterised by xeroph5'tic stunted 

 shrubs and undershrubs. The Sand-deserts have an early spring- 

 aspect like that of the Clay-deserts. They show different landscapes: 

 1. The Barchans, crescent-shaped yellowish dunes of inland sand. 

 They may be naked: Aristida pennata is the first pioneer, later the 

 switch-trees make their appearance {Amniodendron, Calligonum, Sal- 

 sola etc.), and also several hardy herbaceous plants, mostly long- 

 lived annuals, strike root. 2. The Hummock-desert, round sand-hills 

 with a richer Vegetation of herbs, of which many are perennials. 

 The switch-trees are yet found. but they are weaker and lower 

 than in the true shifting desert. 3. The Sand-plains. Here the trees 

 are very low or wanting, and the herbs numerous. 



These three sub-formations show the evolution of the Sand- 

 desert from shifting to more stable through a regional succession 

 (Cowles). 



The Riverside thickets consist of Poplars and other trees and 



