1906] CHRYSLER—NODES OF GRASSES i. 
very slightly from the vertical and do not dip deeply into the central 
cylinder. The xylem consists so largely of tracheids running irregu- 
larly and mixed with parenchyma, that the mass has a considerable 
resemblance to transfusion tissue. Apparently, this region in a 
bundle forms an important water-storing organ. A further peculiarity 
of the bundle at this level is the presence of a distinct bundle-sheath 
or endodermis,? consisting of cells whose walls are reticulately thick - 
ened and suberized. As these larger leaf-trace bundles descend through 
the node, branches from the anastomoses mentioned above extend 
outward between the leaf-trace bundles, and probably anastomose 
with these, though the fusion is not so plain as in A. sativa. Below 
this level the bundles gradually resume the ordinary collateral shape, 
lose their endodermis, and run down in a single circle through the 
internode as already described. The smaller leaf-trace bundles 
also undergo some expansion as they penetrate to the boundary of 
the central cylinder, but throughout their course they may be dis- 
tinguished from the larger bundles, not only by their size but by 
their early turning outward into the cortex and running down to 
the next node as the cortical bundles described above. 
Though it is not plain in A. barbata that the larger leaf-trace 
bundles are joined, soon after their entrance into the stem, by other 
bundles of the node, in A. sativa and in many other grasses it may 
clearly be made out that on each flank of the leaf-trace bundle another 
strand applies itself, swinging through an angle, so that its phloern 
first joins on, then its xylem. In some species, e. g., Arundo Donax, 
two or more bundles join on each flank of the leaf-trace bundle. 
Certain features of the cortical strands are more clearly seen in 
Panicularia americana. The cortical nature of these strands is 
unquestioned, for they run quite outside-the central cylinder, in a 
wide area of lacunar parenchyma (jig. 7). As they reach the upper 
part of a node they anastomose with one another so as to form a 
transverse ring or girdle (jig. 8), which, at a slightly lower level, 
sends branches to the bundles of the central cylinder, forming nearly 
‘or quite amphivasal bundles, though some of them very soon resume 
2 The term endodermis is here used in the general sense employed by VAN 
TieGHEM, rather than in the histological sense proposed by other writers. 
