i ; ne | The External Form of Plants. a 75° 
they are hen called htinidpted (Figs. 106, 107). . All roots 
are more or less branched, and are often clothed with ex- 
tremely delicate root-hairs. If the branches of the root run 
principally near the surface of the ground, they are called 
creeping roots. With reference to their texture, a may be ~ 3 
divided into woody and fleshy.! 
EEE SENT, 
The Stem, in its various forms—to which a great variety ~ 
of names are given from its diverse appearance, though in 
essential points always the same organ—is that part of the 
plant which is constructed for the purpose of bearing the 
leaves, flowers, and fruits. | 
In ordinary language the term is applied to those parts — 
of the plant only which are above ground. But a closer 
examination shows that many plants possess organs which 
must, in accordance with their function, be considered stems, 
but which nevertheless remain, during the whole of their 
« 
<™ -ES 
existence, below the surface of the ground ; and these are ~ 
called underground stems. There are some plants which 
; 2 P i 
! [Any root which results from the development of the radicle or 
-lower extremity of the axis of the embryo is a zormal root; the term 
adventitious root being applied to those of any other origin, z.e. from the 
_ stem, either below or above ground. Aerial roots are usually adven- 
titious, and their purpose is generally to absorb moisture from the. 
atmosphere. The aerial roots, however, of the banyan, Frcus indica, at 
length reach the ground, assume the character of trunks, and give to a 
single tree the aspect of a grove ; while those of the mangrove, Ahzz0-— 
pho: a, which also reach the ground, are true normal roots, resulting 
from the germination of the seed while the fruit is still attached to the 
tree. The roots of Monocotyledons are always adventitious, the radicle _ 
never being developed, as are also those of Cryptogams. The roots of 
parasites, which derive their nourishment from the living tissue ef their 
hosts, may be normal as inthe mistletoe, V7sczm album, or adventitious 
as in the dodder, Cuscuta, where the original normal root which strikes - 
into the soil dies away, and the plant subsequently attaches itself to 
its host by ‘haustoria.’ True roots do occasionally, but very rarely, 
produce leaf-buds (see p. 82). The function of the root-hairs is the 
absorption of liquid nutriment from the soil.—ED. ] 
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