92 



bearing several series of branches. The vegetative branches 

 are annual like the floral ones, and may therefore biologi- 

 cally be regarded as leaves which fall off at the end of the 

 vegetative period. 



The perennial as well as the annual branches are often 

 closely bunched together owing to the formation of new 

 branches year after year at the same place. The younger 

 branch-tips are often pendant and w r ave in the wind (Am- 

 modendron, Haloxylon, Sahola Arbnsciila). 



They have all long roots. The fruits in every case con- 

 tain one or at most a few seeds, and are so formed that they 

 fly or roll easily before the wind, hence one finds them 

 massed together in sheltered places. 



To the bushes and trees given above for the Sand-desert, 

 the following may be added which like Saxaul are rather plants 

 of clay soils and do not thrive so well on pure deep sand: 

 Smirnowia tnrkestana, Astragalus Ammodendron, paiicijngus, 

 imifoliatus, Ephedra alata, Tamarisks and probably others. 



The switch-shaped trees and bushes (and Aristida) are 

 however rarely the only living plants in the Sand-desert. 

 Between the dunes where there is a certain amount of 

 shelter, the soil in many places is sufficiently stabilised for 

 the growth of hardy herbaceous plants. These are not places 

 where there is clay soil between the dunes such belong to 

 the formation of the clay-desert, but where there is sandy 

 soil somewhat sheltered and therefore not shifting. Here grow 

 a number of annual and perennial herbs which are more 

 xerophytic and less halophytic in type than the clay-plants. 

 They occur scattered about, and frequently they have a hard 

 struggle for existence where the sand blows away or drifts 

 over them. 



One of the most frequent is Heliotropium Radula. This 

 like H. sogdianum which also occurs, has a thin horizontal 

 rhizome, sometimes of considerable length (2,5 metres and 

 more), and lying close under the sand-surface; it puts forth 

 numerous aerial shoots, which generally form hairy leaf- 

 rosettes arranged in a row, similar to the rosettes of our Came 

 arenaria. (Fig. 63). Long-jointed shoots bearing inflorescences 



