Hill . — On the Seed ling -Structure of certain Piper ales. 167 
The xylem, small in amount, of the seed-leaves pursues a straight 
course, and comes into contact with the protoxylem of the plumular strands, 
the two then being practically indistinguishable. 
The four epicotyledonary bundles fuse in pairs, to form two large 
pyriform strands. Lower down, the central cylinder loses its oval shape and 
becomes rounded in outline. At the same time the metaxylem becomes less 
abundant, and, at a still lower level, the central xylem gradually takes up 
a position nearer the endodermis ; the smallest elements, however, do not 
occupy an exarch position. Thus a really typical root-structure does 
not obtain ; the plant under consideration resembling, in this respect, 
Pep . maculosa and Pep. tithymaloides. 
Peperomia amplexifolia , A. Dietr. The petiole of each seed-leaf has 
the usual single bundle. These strands are small as viewed in transverse 
sections, each being no larger than one of the surrounding parenchyma 
cells. No bifurcation of the phloem nor rotation of the xylem takes place, 
as in the plants hitherto described. The cotyledonary traces enter the 
axis as normal collateral structures. In one plant it was noticed that 
at the base of the seed-leaf petiole the strands were placed obliquely to the 
dorsoventral line of the cotyledon ; but this did not obtain in the other 
individuals examined. 
Another feature of interest is the fact that the free edges of the bases 
of the petioles of the seed-leaves fuse, so that there is formed a cotyledonary 
tube around the axis. 
The oldest seedling examined possessed two young foliage leaves, each 
having three bundles, one large and central, with lignified elements, and 
two smaller, lateral in position, and more or less merismatic. 
The traces of the youngest leaf enter the axis and fuse with the 
merismatic central cylinder. At a slightly lower level the bundles of 
the leaf are seen alternating with three small merismatic strands, which are 
situated nearer the centre. At the node next below the bundles of the 
oldest leaf enter, so that there result two well-marked zones of bundles. 
Those of the oldest leaf move centripetally, so that at the cotyledonary 
node the strands no longer exhibit a scattered disposition. Fusions now 
take place between the various plumular traces, as a result of which four 
vascular strands are formed. During these changes the cotyledonary 
bundles have entered the axis, and occupy a position one on each side 
of the group of plumular traces. One cotyledon-trace fuses with the 
nearest epicotyl-bundle ; the metaxylem and phloem of both coming into 
contact, and the protoxylem of the seed-leaf being somewhat isolated. 
Further junctions take place between the plumular traces, so that two large 
bundles result. The other cotyledon-trace now fuses up, its phloem 
dividing into two unequal strands, the largest of which joins with the bast 
of the bundle alternate to that with which the first cotyledon-trace fused, 
