Transition from Stem to Root in Palm Seedlnigs. 59 
leaf of the plumule, are now seen at the cotyledonary node. They 
are quite unlignified and only partially differentiated (Fig. 5, vi.) 
A little higher the cotyledon sheath with its six or seven 
bundles is separated from the plumule, which now contains the 
small but well developed upward prolongations of the root-bundles, 
continuous with the gradually differentiating and lignifying stem 
bundles (Fig. 5, vii.) 
In order as far as possible to simplify the description of this 
somewhat complicated series of changes, the behaviour of the 
xylem alone has been considered The phloem during the transition 
loses all connection with the xylem and runs in the form of more 
or less distinct strands in the parenchyma which separates the 
xylem bundles from the endodermis. Some of these are continued 
into the lower ends of the phloem bundles of the stem in the 
normal position of collateral bundles. Others are distributed to 
the xylem groups prolonged upwards from the root bundles into 
the cotyledon-stalk. 
The bundles in the cotyledon sheath are multiplied distally by 
bifurcation, so that as many as twelve bundles may be found. The 
ground tissue at the base of the sheath, and also distally, is rather 
dense, but at a region about one third of the way up it is much 
more open, and round some of the individual bundles in this region 
a ring of cuticularized cells is found. Sometimes this ring is 
incomplete round the outside, i.e. externally to the phloem it is well 
developed, but internally, opposite to the protoxylem, it may be 
absent. A similar structure is found in Livistona mauritana, and 
is described at greater length under that heading. 
Livistona mauritana Wall. 
Only a fairly advanced seedling (Fig. 6) could be obtained. 
The cotyledon-stalk is very long and the sheath somewhat 
bulky. For convenience the structural changes will be traced 
from above downwards in this plant. A section at 5 (Fig. 6) 
shows the bundles scattered throughout the whole section of the 
cotyledon, (Fig. 8, i.) As many as fifty of these bundles may be 
present in this region. They are seen singly and in all stages of 
fusion with one another. Their function is that of conducting to 
the growing seedling the reserve food material, now rendered 
available in the soluble form by the ferments secreted in the 
cotyledon. In accordance with these functions but little xylem is 
present in the bundles. The phloem groups are well developed, 
and are enclosed in very dense sclerenchymatous sheaths. The 
bundles lie in a ground mass of typical parenchyma. 
