104 Ford.— The Anatomy of 
small inconspicuous steles (Fig. 3 , b 2 ) are irregularly scattered 
in the parenchymatous tissue. The large outer bundles vary 
much in shape, some being circular in outline, others oval or 
long and narrow, or slightly S-shaped. Both the large and 
small steles anastomose with each other at different levels. 
The bundles run more or less obliquely in the stem, and it 
is only at some levels that really transverse sections can be 
obtained, and this again is generally a matter of chance. 
Fig. 6 represents a photograph taken of one of the large outer 
steles. The structure is roughly the same as that met with 
in the petiolar vascular strands, but everything is on a much 
larger scale and no surrounding ring of sclerenchymatous 
tissue is present. The xylem lies in the centre, and is made 
up of scalariform tracheids with small islets of parenchy- 
matous cells scattered among them. The protoxylem ( px ) 
is found on the outer edge of one side of the xylem, lying 
between the latter and the sieve-tubes. Owing to the small 
size of the individual elements of the stele, the protoxylem is 
often difficult to identify, but its position, as stated above, 
is clearly seen in sections of steles near the apex. At this 
level none of the tracheids are differentiated but those com- 
posing the protoxylem, and these, in consequence, stand out 
conspicuously. The bundle is very markedly bicollateral, the 
large sieve-tubes (Fig. 6 , st ) forming conspicuous elements on 
each side of the xylem ; the characteristic granules on the walls 
of the tubes are also clearly seen. Beyond the sieve-tubes 
some ordinary parenchymatous cells are found, amongst which 
elements are present which probably represent the protophloem 
(Fig. 6 ,//). The cells have slightly thickened walls which 
are darker in colour than those of the ordinary parenchymatous 
tissue, and some have a more or less crushed appearance. 
This tissue is the only one present which can in any degree 
be compared to the protophloem, and if it be regarded as 
such then the stem-bundles differ from those in the petiole by 
having this tissue developed on both sides instead of one side 
only of the xylem. Parenchymatous cells are scattered about 
irregularly, separating the sieve-tubes from the xylem in 
