— 106 — 



but because at the present time they agree on general lines 

 as regards soil and growth-forms. More thorough knowledge 

 of the vegetation would perhaps lead one to designate the 

 different types of sandy desert as formations, or even to 

 create more, e. g. a special formation for the vegetation of 

 the valleys between the sand-hills. If one followed the con- 

 cepts of Crampton in a recent paper — published subsequent 

 to the Danish edition of our memoir — , then the different 

 types would be regarded as formations: the Barchan desert 

 would be a migratory (or neogeic) formation whose substra- 

 tum "owes its features to recent geological processes", where- 

 as the Desert of the Sand Plains would be termed a stable 

 (or palaeogeic) formation; presumably the Hummock desert 

 would also be a stable formation. 



Though brought into existence in a different way, the 

 development of the Sand-desert is similar to that of the dune- 

 territories of northern Europe. 



The Spring-aspect of the Sand-desert I hardly know 

 from personal observation, hence the following account is 

 mainly based on plant-lists and descriptions borrowed from 

 KoRSHiNSKY and Radde (1899). The Spring-plants are mostly 

 found in the stable sand-desert, but they may also occur in 

 the more shifting desert, especially in depressions where the 

 moisture is greater, the clay-content larger, and the surface 

 therefore firmer. Wherever the seeds are carried, there they 

 must germinate when spring comes, and even on loose sand 

 and under unfavourable conditions the ephemeral plants may 

 still succeed in maturing their seeds; their precocious develop- 

 ment comes here to their aid and is indeed their only means 

 of preservation. 



On stationary sand the spring-vegetation may be com- 

 paratively rich, yet nowhere does it form a carpet. 



The only species which locally attempt to form a green- 

 sward are Carex physodes and Capsella procumbens. The former 

 has been frequently referred to already (see p. 97) as it plays 

 a great part in binding the sand. It is already in flower in 

 March and bears fruit in April, the fruiting ear is large and 

 inflated so that it is easily I'olled along by the wind. Cap- 



