— 239 — 
The hairs on the upper surface are comparatively few, but 
thick and stiff; they are white and each one occupies a 
white circular base. On the lower surface these hairs are 
very numerous. The white flowers are out in May. 
Heliotropium Radula, so far as it has been possible to 
determine the frequently sterile light-shoots, seems to have 
the same mode of growth and the same form of leaf and 
hair-coating as H. sogdianum. The hair-coating is, however, 
somewhat closer. 
The leaf of H. sogdianum is isolateral. The epidermis 
is one-layered, densely hairy (with hair-cystoliths, see H. 
dasycarpum p. 222), and with slightly sunk stomata on both 
sides. There are about two layers of short, starch-filled 
palisade cells on each side. The veins are surrounded by 
translucent cells. 
Aristida pennata Trin. 
This sand-binding grass has been already dealt with 
(p. 81-83). The thick, shrubby growth of the plant and its 
power of forming lateral shoots, which add to the tufts and 
when buried by the sand form new ones, makes this plant 
the “Conqueror of the Sand-desert” (ANTONOW) and the most 
valuable of all sand-binders. 
It has been already recorded and illustrated (fig. 9) that 
the roots are encased by a sand-stocking. Within this 
stocking the root lies loose, ‘‘wie das Bein in der Hose oder, 
besser und ästhetischer ausgedrückt, wie eine Phryganeen- 
larve in dem selbst gebauten Gehäuse” (VoLKENS p. 26). 
VOLKENS points out that this sand-stocking is formed by the 
roots - hairs cementing the sand-grains together, and he is of 
opinion that its function is to protect the rools against 
evaporation. This is confirmed by the fact that in grasses 
provided with a sand-stocking, there is no cork or other 
corresponding means of protection. 
My observations show that the root, which sits loose 
in the sand-stocking, is devoid of corlex. It is enclosed in 
a thick-walled pericycle consisting of several layers of prosen- 
chymatous cells with numerous pores and containing starch; 
