summer-aspect; then in its spring-aspect, which greatly re- 
minds one of that of the clay-desert. 
In the more shifting deserts there are areas with nothing 
of interest to the botanist. Hills and valleys of sand, not 
even a stone, nothing but sand. This is sorted out by the 
wind, the coarser and darker sand covers the gentle slopes 
of the windward side and the crests of the wind-billows. 
while the finer and lighter sand is found on the steeper lee 
side and in the valleys. These variations in shade increase 
the relief of the surface. 
The first pioneer of the vegetation is “Selin”, Aristida 
pennata Trin.'), so aptly called by ANronow the Conqueror 
of the Sand-desert. 
Aristida pennata takes first place as a sand fighter. It 
grows quickly, and gives off many roots, many leaves, many 
branches, while its internal structure enables it to endure 
drought and sand-drift. It is more fully described later 
(chap. 13), but features of its biology may be indicated now. 
After germination it forms a number of basal scale-leaves 
through whose sheaths the fibrous roots break out. The foli- 
age leaves follow on short internodes so that their sheaths 
form a “Tunic’’ (Hacker), the one sheath lies over the other, 
with only a short apex free, so that the expanded leaf-blades 
are close-set one over another. In the axils of the scale-leaves 
lateral shoots quickly appear covered by their “tunics”. The 
young plant thus forms a close tuft with the oldest shoots 
in the middle (fig. 9), and as the tufts grow older they be- 
come coarse leafy tussocks half a metre or more in diameter. 
When the sand drifts over, the plant pushes upwards with 
longer internodes, and new lateral shoots with basal roots 
are continually being formed. so that the plant is fixed in 
the sand almost right up to the surface. The lateral shoots 
1) This plant has been named at different times A. pungens Desf., 
A. pungens var. pennata, A. pennata and sometimes it has been regarded as 
two species A. pennata and A. pungens. It is certainly closely related to 
the Sahara form A, pungens, being distinguished from it mainly by its more 
slender growth and by longer branches of the panicle. I do not think there 
is any reason for calling specimens with shorter panicle-branches A, pungens. 
The Transcaspian specimens are certainly all the same species 
6 
