1 66 Hill . — On the Seedling- Structure of certain Piper ales. 
tracheae, and at a lower level they may be separated from them by two 
or three parenchyma cells. Finally, however, the two protoxylem groups 
come into contact with the metaxylem elements, which range themselves in 
line, so that a typical diarch plate obtains. 
In older seedlings the epicotyledonary axis has six bundles, three 
derived from each of the two foliage leaves, arranged roughly in a circle. 
Much anastomosing and redistribution take place between these traces, as 
a result of which there are formed two strands, separated one from the other 
by parenchyma, and situated at right angles to the line joining the two 
cotyledonary bundles. As soon as this arrangement is effected the seed- 
leaf traces enter the central cylinder in the manner already described. 
In these older seedlings more metaxylem is derived from the plumule 
than from the cotyledons, but these elements rapidly disappear, so that 
at the slightly lower level the lignified elements obtaining are those derived 
from the seed-leaves. 
Peperomia polystachya , Hook. The material of this plant was not 
entirely satisfactory, inasmuch as very few of the seedlings retained their 
cotyledons. Thus it was not possible to follow the course of the bundle 
from the cotyledon to the petiole. Sufficient, however, was made out 
to indicate that, as regards the behaviour of the bundles of the seed-leaves, 
this species occupies a position intermediate between Pep. pellncida and 
Pep. ample xif alia. At the base of the petiole of each seed-leaf a single 
strand may be seen with its protoxylem in an endarch position, and its 
phloem spread out tangentially and somewhat bilobed. 
Immediately before its entry into the axis the metaxylem may be 
seen to be separated into two masses by parenchyma, but no rotation 
of the protoxylem can be made out. 
When the plumule is well developed the bundles of the third internode 
are markedly arranged in two whorls, six strands in the outer, and four in 
the inner. At the node below the incoming traces fuse with certain of 
these bundles, and anastomoses occur between the vascular strands of the 
two whorls, so that in the second internode there obtain three bundles 
in the inner and six in the outer ring. Similar junctions take place at the 
node below, resulting in the formation of a single strand centrally placed 
and surrounded by a zone of five. These bundles join up with one another, 
hence there result four epicotyledonary strands, two on one side and 
a similar pair on the opposite side of an imaginary line joining the two 
incoming cotyledonary traces. 
As the seed-leaf bundles approach the centre of the axis the phloem 
of each separates into two masses which fuse with the phloem of the nearest 
plumular trace. This branching of the cotyledonary bast is sometimes 
very unequal, for nearly all the phloem from one bundle may go to one of 
the pair of plumular bundles. 
