Hill. — On the Seed ling- Structure of certain Piper ales. 169 
On comparing these changes with those obtaining in Arum maculatum \ 
many points of similarity are to be found, more especially as regards 
the zoning and fusions of the plumular traces, and the method of union 
of the cotyledon-bundles with these strands. But, at the same time, it 
must be pointed out that a certain amount of variation obtains in Pep. 
amplexifolia : thus, in a seedling of about the same age as the one just 
described, it was found that, although the youngest foliage leaf contributed 
the normal number three, only one bundle entered the axis from the oldest 
foliage leaf, so that instead of having two zones of bundles the axis had an 
irregular ring of four strands. 
At a level slightly below the cotyledonary node intercommunications 
take place between the plumular traces, resulting in the formation of two 
bundles somewhat obliquely situated, and with their xylems separated 
by a thin layer of parenchyma. This arrangement is effected immediately 
before the entry and fusion of the cotyledonary traces, which enter the axis 
and travel to the central vascular strand as collateral structures. Imme- 
diately before fusion the phloem of each branches to the right and left 
of the xylem, and comes into contact with the bast of the epicotyl-bundles, 
while the xylem behaves in the manner already described. 
Both in this and in other species it is sometimes found that the phloem 
of the cotyledonary traces divides into two very unequal strands, so that one 
side of the vascular cylinder may sometimes receive nearly the whole 
of the phloem of one seed-leaf bundle. 
Peperomia tithymaloides , A. Dietr. All the seedlings examined had 
a well -formed plumule with three foliage leaves. The structure of the 
epicotyl is similar to that of Pep. amplexifolia , as regards the definite zoning 
of the bundles, and the anastomosing of these structures at the nodes. The 
chief difference lies in the fact that the number of the leaf traces is rather 
more variable in Pep. tithymaloides. Thus, in one plant, the youngest leaf 
had four traces, the next youngest three, and the oldest only one ; three 
strands, however, appear to be the typical number. 
The cotyledonary bundles are small, single, and collateral (Fig. 10); 
and, as in Pep. amplexifolia , and the species described hereafter, there is 
no bifurcation of the phloem, nor rotation of the xylem. Immediately 
before the entry of the seed-leaf traces the plumular strands are arranged 
in an elliptical zone, three being on one side and three on the opposite side, 
the largest of each group being bounded by the smaller. The cotyledonary 
bundles enter and occupy positions corresponding to the foci of the ellipse. 
The phloem of these branches to the right and left of the xylem, and, 
passing inwards, fuses with the corresponding tissue of the plumular strands, 
while the metaxylem travels towards the centre and effects a junction with 
1 Scott, R. and Sargant, E. On the Development of Arum maculatum from the Seed. Ann. 
Bot., xii, 1898. 
