THE DIFFERENTIATION OF THE PLANT-BODY 27 
The same tissues serve for transport in the Monocotyle- 
dons, and in the Vascular Cryptogams, though the mode of 
arrangement of the elements is altogether different from 
that of the Dicotyledons. 
In those vascular plants which live in water, and parti- 
cularly in those which are totally submerged, there is no 
need for so elaborate a transport 
system, as water can be readily 
absorbed by the general surface. 
We find two modifications of 
structure in such plants; the 
epidermis is hardly at all cuti- 
iz = 
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Sara 
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SAG 
Fic. 27.—DiacRamM OF THE COURSE 
OF THE VascuLaAR BUNDLES IN Fic. 28.—DistrRrBurioN OF THE 
an HeERpacrous DicoryLEpo- VascuLaR BuNDLES OR VEINS 
nous Pant. tn a Fortace Lear. 
cularised, so that water can pass from the exterior into its 
cells ; while the vascular bundles are comparatively feebly 
developed, the woody part of them being particularly small. 
The third requirement of a plant of considerable mass, 
especially if it has a terrestrial habitat, we have seen to be 
a power of resisting such external forces as would lead to 
its uprooting, which must be combined with a considerable 
degree of flexibility, at any rate at the extremities of the 
body. This combination of rigidity and flexibility has been 
secured in various ways, varieties of both the form and 
the structure of the plant being concerned in it. In the 
simplest plants but little differentiation of the body is 
