174 Scott, — On some points in the Anatomy of 
here 1 . Each group of internal phloem belongs definitely to 
one of the leaf-trace bundles, and accompanies the latter on 
its exit into the leaf. 
Before considering the modifications of structure which 
subsequently arise in certain parts of the stem we will trace 
the relation between the bundle-systems of stem and root, 
for this plant illustrates with diagrammatic clearness the 
changes through which bicollateral bundles pass in the tran- 
sitional region. 
The two 2 obcordate cotyledons each contain four vascular 
bundles in the petiole, all of which, like those of the leaves 
generally, are bicollateral. The two median bundles are 
of large size, and lie close together. The two small lateral 
bundles are widely separated from them. On entering the 
axis the bundles of each median pair at once turn their 
protoxylem-groups towards each other, and pass down through 
the long hypocotyl to the root. The lateral bundles of the 
cotyledons on entering the hypocotyl approach each other 
so as to form two other pairs, at right angles to the former, 
each lateral pair being thus made up of one bundle from each 
cotyledon. These bundles also turn their protoxylem-groups 
towards each other and can only be distinguished from the 
median pairs by their position. The median pairs are further 
from the centre, the major axis of the elliptical pith passing 
through them, while the minor axis coincides with the position 
of the lateral pairs. The opposite median pairs are separated 
by about 14, the lateral pairs by about 9 pith cells. Lower 
down the pith of the hypocotyl becomes circular, and here all 
the four pairs of bundles are in all respects similar. The 
diagrammatic section (Fig. 2) is taken at a point where the 
pith is still somewhat elliptical, C-C being the median plane 
of the cotyledons. 
The bundles of the plumular leaves fuse with the lateral 
1 Cf. Solereder, Ueber den systematischen Werth der Holzstructur bei den 
Dicotyledonen, 1885. 
2 Occasionally three cotyledons are developed, but I did not investigate these 
exceptional seedlings. 
