170 Hill. — On the Seedling-Structure of certain Piper ales. 
the xylem of the plumular bundles, thus forming a somewhat irregular 
plate. Concurrently, the three epicotyledonary bundles of each side fuse, 
so that there result two large collateral structures, one on each side. The 
two protoxylem groups derived from the cotyledons retain their relative 
and isolated position for some time, having a crushed appearance, some 
being almost entirely obliterated (Fig. ji). Ultimately, these protoxylem 
groups come into contact with the xylem of the plumular strands ; at 
a still lower level an endodermis is differentiated, and the vascular tissue 
decreases in amount (Fig. id). 
Peperomia maculosa , Hook. The transition phenomena are essentially 
the same as in the last species dealt with. The differences which obtain 
are unimportant, and are briefly as follows. At the level of the insertion 
of the seed-leaves the epicotyledonary strands are five in number, three in 
one group and two forming the corresponding opposite group ; whereas 
in Pep. tithymaloides there are six bundles arranged in threes. Further, the 
phloem of the seed-leaf traces branches somewhat earlier in Pep. maculosa. 
And again, in the last-named plant, all the xylem, with the exception 
of one element of the cotyledonary strands, passes to the centre of the 
vascular cylinder, fusing one with the other and with the w r ood of the plu- 
mular bundles, which, by this time, have formed two large pear-shaped 
structures. The elements left behind occupy a solitary position well 
towards the periphery of the stele, one on each side, and they indepen- 
dently follow an undulating course downwards ; so that a diarch plate, 
small and not well defined, may result at one level, while at a lower level 
the plate may exist on one side and not on the other. 
One seedling exhibited a curious anomaly, which resulted in a seem- 
ingly unnecessary redistribution of vascular tissue. 
Towards the base of the axis a strand of phloem was given off from 
one of the phloem masses of the central cylinder. The strand followed 
a downward spiral course, passing on the outside of the protoxylem, and 
receiving elements from the metaxylem in its passage, thus appearing 
as a collateral structure, but quickly becoming somewhat more root- like by 
a rearrangement of the phloem ; but instead of emerging as a lateral root 
it pursued its spiral course, circling around to the side from whence it came, 
and ultimately fused with the vascular cylinder. 
It may be added that a lateral root does, in this species and in others, 
sometimes arise directly opposite a phloem group. 
From the foregoing account it is clear that the species of Peperomia 
examined fall into two divisions. In the first may be placed Pep. 
eburnea and Pep. pellucida , both characterized by the occurrence of a 
certain amount of rearrangement in the cotyledonary bundles, while still 
contained within the petiole ; and in the second, Pep. polystachya , Pep. 
