208 PLANT ANATOMY. 
tracted. The transverse sections of these cells of the nucleus- 
sheath therefore appear differently, according to the thickness of 
the thickened layers, and thereby afford serviceable characteris- 
tics for the recognition of the several varieties of a drug.’ 
While the nucleus-sheaths in most of the examples that have 
been cited are built up of a single row of uniform cells, the 
root-stocks of the Zingiberacew deviate considerably in this 
respect. Indeed, the endodermis of the rhizomes of Curcuma, 
Galanga, Zedoaria, and Zingiber is composed of several rows of 
cells * (Fig. 125). 
3. The Absorbing System. 
The absorption of inorganic salts from the soil is effected by 
the aid of the roots and especially by means of the root-hairs. 
The latter, which are true trichomes, by forming manifold pro- 
tuberances, become most intimately attached by their growth 
to the particles of the soil. | 
Root-hairs are found on but few officinal roots (for instance, 
Sarsaparilla, Fig. 126). In most cases they are broken off in 
the process of unearthing them, or they may have been already 
absent at the-time of collection, since the formation of root- 
hairs only takes place in definite and young parts of the root. 
For the absorption of organic nourishment, the phanerogamous 
parasites penetrate the host-plant by means of the so-called 
haustoria (as in the case of Cuscuta). To these haustoria cor- 
respond the surfaces of the cells lying close to the endosperm, 
which consist mostly of palisade-shaped cells with protuberances 
resembling root-hairs, and which are especially met with on the 
scutellum of the Gramineew. They serve for imbibing the re- 
serve substances. 
In order to convey nourishment to the embryo during germina- 
‘Compare Schleiden, « Beitrige zur Kenntniss der Sarsaparilla.” | 
Archiv der Pharm., 1847, Arthur Meyer, I bid., 218 (1881), p. 280 et seq. 
Berg’s ** Atlas,” Plate iv, Flickiger, “ Pharmakognosie,” p. 295. 
-? Compare Arthur Meyer, Archiv der Pharm., 218 (1881), p. 419. 
