I 12 
Ford . — The Anatomy of 
The endodermis and pericycle are clearly seen (Fig. 2, e,pe) 
and the protoxylem-groups may or may not touch the 
pericycle. By the further differentiation of tracheids between 
the two original groups, a solid band of xylem is formed 
(Fig. 3, x). The phloem, which in a later stage is found on 
each side of the band of xylem, is as yet undifferentiated, and 
cannot be distinguished from ordinary parenchyma. In the 
young plant from which Figs. 2 and 3 were obtained, no 
further stages of development were found, but in Fig. 4, 
which was taken from the base of a considerably older plant, 
a stage is seen corresponding in arrangement with that 
already described in Fig. 3, though everything is on a larger 
scale. Following a series of transverse sections of this stem 
from the base upwards, it is seen that, by the further develop- 
ment of tracheids, a more or less solid central xylem-strand is 
found with phloem (Fig. 5, st ) lying on both sides, the sieve- 
tubes showing, as a rule, the characteristic dots on their 
walls. One or more ordinary parenchymatous cells (Fig. $,pa) 
are generally mingled with the tracheids, but their presence is 
not constant. In some cases the xylem-strand becomes horse- 
shoe-shaped before reaching the stage represented by Fig. 5, 
but this again is not a constant feature. In other plants, 
younger than the one under consideration, the stem remains 
monostelic throughout, the single solid strand giving off leaf- 
traces at intervals. 
In the plant in question, however, the single stele divides into 
two, and throughout the remaining portion of the stem more 
than one stele is always present. In Fig. 6 the xylem of the 
stele is about to divide into tw r o strands which are seen in 
Fig. 7, still enclosed by a common endodermis. The two 
strands are separated by large thin-walled cells containing 
somewhat disorganized nuclei ; this tissue is very similar in 
appearance to that seen in the main mass of parenchyma of the 
stem in which the bundles lie embedded. One of the two 
xylem-strands resulting from this division gives off almost 
immediately a leaf-trace (Figs. 7 and 8, /). The endodermis 
breaks and unites very rapidly round each strand. 
