40 THE ROOT. 
20. The extension of the root enables some plants to per. 
form an important office in the economy of nature, namely, pro- 
teeting banks of rivers and coasts where there is much loose 
shifting sand, from being broken down by the winds or 
waves, and also preventing the neighbouring fields from being 
overrun with sand. The roots of many of the grasses 
(Carex arenaria, Elymus arenarius, Ammophila arundinacea, 
and others) run to a great extent under ground; and, being 
much entangled there, bind the loose sand; and form a 
rent bank, which is better able to resist the action of | 
wind or encroachments of the ocean. In many places. 
England, the growth of these plants is encouraged with th 
view ; and acts of Parliament have been passed for their 
_ servation. 
121. The stem and branches also possess this property 
throwing out rootlets: if a branch be placed in the earth, or 
surrounded with earth on the tree, an incision being made 
the bark, it will emit rootlets from its sides, and become, 
properly treated, an entire and independent tree ; hence 
propagation of plants by slips and by layers. Many of 
_ Grasses, as Indian Corn (Zea mays), and the Sugar C; 
- (Saccharum officinarum), emit from the knots on the 
these parts are surrounded with moist earth, r 
ce epithe. of producing new plants. In this way the 
_ Cane is propagated. The famous Banyan tree of India : 
fords a striking illustration of the power of branches 
throwing out roots. These descend perpendicularly to’ 
earth, where they take root, spread in the soil, and supp 
the growth of the tree in the usual manner. rt I 
__ ithas taken root, and becomes another stem, giving m 
‘ment and firm support to the part with which it is co 
ie ee et ey ah nin ee 
trunk. New roots descend from these | ; 
eoume new stems, and thus One. trons 
of ground. One Banyan t 
t noon 1116 feet in 
