28 Lang .— Studies in the Morphology and 
of spiral or reticulate tracheides, and may fail to develop in some regions 
of the stem. The leaf-traces in the first branch showed adaxial completion 
of their xylem, while in the second branch this was only slightly indicated. 
Another interesting difference, for comparison with young plants, was that 
the first leaf on the one branch was an arrested structure, while in the 
second branch it was shown by its vascular supply to have been normal. 
Anatomy of young plants. The anatomy of young plants developed 
from embryos will be dealt with as briefly as possible. The main facts 
are recorded by Campbell and myself in the existing literature, but not 
in the form required for comparison with the branches and the rhizomes of 
adult type. What is further necessary may be brought out by following 
a series through part of a well-developed young plant, such as that figured 
in outline in the previous paper of this series. 1 Such a plant would show 
the large foot at the base, the primary root with its vascular system con¬ 
tinuous with the base of the stem stele, but not in the same straight line 
as this, and the strictly dorsiventral construction of the further growth. 
The plant actually selected for description had borne four expanded leaves 
dorsally, and a number of roots (in addition to the differently placed 
primary root) ventrally. 
Transverse sections of this plant at various levels are represented in 
Text-fig. 7, the external outline, the endodermis, and the xylem only being 
shown. The scale did not allow of a distinction being made in these figures 
between the inner and outer xylem. In Text-fig. 7, A, the continuity 
between the stele of the first root and the base of the stem-stele is seen, and 
this root is seen to differ from all the later ones in standing on the morpho¬ 
logically dorsal side of the plant. B and C show the hypocotyledonary stele, 
while D, E, F, G show the departure of the first leaf-trace, the slit leading 
down to the first vestigial bud being evident in G. The second root is seen 
in F. The departure of the second leaf-trace extends from H to K, the last 
section passing through the vestigial bud ; L shows the third root and the 
preparations for departure of the third leaf-trace, while in M this trace is 
seen with its axillary canal. In N the fourth leaf-trace is distinct from the 
stele, and the attachment of the fourth root is seen. Beyond this, the 
stele passes into a more meristematic condition, the last tracheides visible 
in P being a dorsal group in relation to the young fifth leaf, and a ventral 
group belonging to this region of the stele ; in connexion with this, the fifth 
root is developing. 
The more important structural features of the stele of this plant are 
illustrated by Photos 40-46, on PL III. The xylem of the hypocotyl 
exhibited a central group of tracheides surrounded by a more or less 
definite zone of somewhat larger tracheides. This zone is rather irregular 
at the level figured (PI. Ill, Photo 40), but became more regular and closer 
1 Ann. of Bot., xxviii, p. 30, Text-fig. 9 A. 
