THE VEGETATIVE ORGANS OF PLANTS. 265 
taching to them a ball or pot of earth. The striking out 
of roots from the layer is in many cases facilitated by cut- 
ting half off, twisting, or otherwise wounding the stem at 
the point where it is buried in the soil. 
The ¢illering of wheat and other cereals, and of many 
grasses, is the spreading of the plant by layers. The first 
stems that appear from these plants ascend vertically, but, 
subsequently, other stems issue, whose growth is, for a 
time, nearly horizontal. They thus come in contact with 
the soil, and emit roots from their lower joints. From 
these again grow new stems and new roots in rapid suc- 
cession, so that a stool produced from a single kernel of 
winter wheat, having perfect freedom of growth, has been 
known to carry 50 or 60 grain-bearing culms. (Hallet, 
Jour. Roy. Soc. of Eiiz., 22, p. 372.) 
Subterranean Stems.—Of these there are three forms 
agriculturally interesting. They are usually thought to be 
roots, from the fact of existing below the surface of the 
soil. This circumstance is, however, quite accidental 
The pods of the pea-nut ripen beneath the ground—the 
flower-stems lengthening and penetrating the earth as 
soon as the blossom falls; but pea-nuts are not by any 
means to be confounded with roots. 
Root-stocks,—As before remarked, true roots are desti- 
tute of buds, and, we may add, of leaves. This fact dis- 
tinguishes them from the so-called creeping-root, which is 
a stem that extends just below the surface of the soil, 
emitting roots throughout its entire length. At intervals 
along these root-stocks, as they are appropriately named, 
scales are formed, which represent rudimentary leaves. 
In the axils of the scales may be traced the buds from 
which aérial stems proceed. Examples of the root-stock 
are very common. Among them we may mention the 
blood-root and pepper-root as abundant in the woods of 
the Northern and Middle States, and the quack-grass, 
12 j 
