THE TRANSPORT OF WATER IN THE PLANT 75 
whose innermost layer, the endodermis, are often peculiarly 
thickened, in much the same manner as those of the 
exodermis already described (page 25). This thickening is not, 
however, usually very marked in the region of absorption. 
At certain places round the periphery of the stele of the root, 
the woody strands (fig. 56, Sp) may be seen. These are in 
contact with the succulent and turgid parenchyma which has 
been filled with water in the way described, and consequently 
the hydrostatic pressure which has thus been set up is brought 
Inia. 56.—Srction or Root, sHowina Roov-HAIRS ABUTTING ON THR 
PARENCHYMA OF THE CoRTEX, AND THE Woopy Srranps, Sp, oF 
THE Steve. (After Kny.) 
to bear upon the walls of the woody vessels which constitute 
the greater part of those strands. These form the lower 
portions of continuous open, or nearly open, tubes, which 
extend from the roots to the leaves; at the time when the 
absorption of the root-hairs and cortex is greatest these 
vessels are empty, or nearly so, and the effect of the hydro- 
static pressure on their walls is to force the water from the 
turgid cortex into the walls and cavities of the vessels. 
How the water is distributed is not fully known; we have 
seen that lignified cell-walls have a certain power of taking 
up water, and of passing it on with considerable rapidity, 
so that part of it may be expected to remain in the walls. 
Part, however, passes through into the cavities of the vessels, 
