— 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 
Korsuinsky 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 rolled along by the wind. Cap- 
