THE VEGETATIVE ORGANS OF PLANTS, 249 
Bean (Phaseolus multiflorus) 6 inches of mercury. 
Nettle - - - - 4 « ss 
Vine - - - - 29 = 
Seat of Absorptive Force.—Dutrochet demonstrated 
that this power resides in the surface of the young and 
active roots. At least, he found that absorption was ex- 
erted with as much force when the gauge was applied to 
near the lower extremity of a root, as when attached in 
the vicinity of the stem. In fact, when other conditions 
are alike, the column of liquid sustained by the roots of a 
plant is greater, the less the length of stem that remains 
attached to them. The stem thus resists the rise of liquid 
in the plant. 
While the seat of absorptive power in the root lies near 
the extremities, it appears from the experiments of Ohlerts 
that the extremities themselves are incapable of imbibing 
water. In trials with young pea, flax, lupine, and horse- 
radish plants with unbranched roots, he found that they 
withered speedily when the tips of the roots were immers- 
ed for about one-fourth of an inch in water, the remaining 
parts being in moist air. Ohlerts ‘likewise proved that 
these plants flourish when only the middle part of their 
roots is immersed in water. Keeping the root-tips, the 
so-called spongioles, in the air, or cutting them away alto- 
gether, was without apparent effect on the freshness and 
vigor of the plants. ‘The absorbing surface would thus 
appear to be confined to those portions of the root upon 
which the development of root-hairs is noticed. 
The absorbent force is manifested by the active rootlets, 
and most vigorously when these are in the state of most 
rapid development, For this reason we find, in case of the 
vine, for example, that during the autumn, when the plant 
is entering upon a period of repose from growth, the ab- 
sorbent power is trifling. The effect of this forcible en- 
trance of water into the plant is oftentimes to cause the 
11* peeks 
