



70 - FLOWERING PLANTS 
lateral roots are in all respects similar to the main root. It 
must be remembered that, although the arrangement of 
bundles in the stem differs from that of the root, there is no 
break in the continuity of the tissues, for the wood bundles 
of the root twist on themselves, so that they come to be on 
the same radii as the bast bundles, and the protoxylem which 
was external in the root becomes internal in the stem. Be- 
sides that, the bundles of the root bifurcate, so that generally 
there are twice as many in the stem as in the root. 
Adaptation °° far the roots of Mesophytes have alone been 
of Structure described ; it will be seen that their structure is 
to Function. 6x actly adapted to the functions they have to per- 
form, which are mainly three : 
1. To fix the plant in the 
soil. . 
ya 2. To absorb water and 
aw >. food-substances from the soil 
a —the work of the root-hairs. 
a 3. To conduct the sub- 
| _ stances thus absorbed to the 
Dn opt S —  stem—the function of the 
a A) is 4 fibro-vascular tissue. 
i «k The structure of the roots 

oe -. be especially noticed. They 
i : have little swellings which 
a4 | are produced by a fungus. 
\\ ——~~~—s* This ‘fungus makes use of 
| : the free nitrogen of the 
atmosphere, building up some 
Fic, 40.—LecuMinous Roor., compound of nitrogen, which 
: it hands on to the plant 
(“Elementary Botany,” pp. 123, 124). 
The roots of Hydrophytes, where present, differ very much 
from those of Mesophytes; the wood and bast are very much - 
reduced for two reasons: the plant has no strain to bear, and 
therefore does not need the support of these tissues; and, 

4 ss \ a of leguminous plants should » 
