260 Scott and Sargant. — On the Pitchers of 
various kinds finds its way into the pitcher, possibly washed 
there by rain from the bark of the tree on which the plant is 
growing. This detritus forms a rich natural soil at the bottom, 
or on the sides of the pitcher, and into this soil the rootlets 
direct their growth. Where a thin layer of humus coats the 
inside of the pitcher, the rootlets apply themselves closely to 
this surface, becoming flattened, and often acquiring a some- 
what dorsiventral structure. 
The pitcher-roots, as we should expect, do not simply 
absorb water, but are also able to make use of the supplies of 
food with which the soil in the pitcher provides them. The 
root-hairs attach themselves firmly to particles of humus, and 
in fact behave just as root-hairs in an ordinary soil would do 
(Fig. n). 
The anatomy of the pitcher-root presents some points of 
interest. The vascular cylinder of its main axis is pentarch 
or tetrarch. In the specimens from Java the wood of the 
mature root extends to the centre, so that there is no pith. 
The wood consists of spiral vessels (limited to the protoxylem), 
tracheides with bordered pits, and xylem-parenchyma. The 
phloem is well-developed and normal, the pericycle is one or 
two layers in thickness. The cortex of the root is persistent, 
no internal periderm having been formed in any of the speci- 
mens observed. The cortex contains laticiferous cells, crystal- 
sacs with calcium oxalate in clustered crystals, and numerous 
sclerotic cells. The latter are usually limited to the outer 
cortical layers, where they form irregular groups, as shown in 
Fig. io. These cells are often thickened almost to the 
obliteration of their lumen, with narrow pits. The short cells 
have square or slightly oblique walls. They do not form long 
continuous series in the longitudinal direction, and are some- 
times quite isolated. They can scarcely contribute much to 
the mechanical strength of the root, and in fact no great 
strength is needed. They harden the external cortex, how- 
ever, and may possibly serve a protective function. 
Outside the layer containing the sclerotic cells is the 
exodermis, which in the mature parts of the root forms the 
