Stem to Root in the Vascular System of Seedlings. 637 
the protoxylem-groups are external. The lateral groups px z 
and px% have fused with each other. The lateral groups 
px% and px£ are on the point of fusing. The stele is already 
practically that of a root, and is surrounded by an endodermis 
( F ig. 6 ). 
It is to be regretted that the three series of sections which 
have been cut through the hypocotyls of three separate seed¬ 
lings have all been more or less damaged in preparation. 
The thin-walled tissues in all are crushed and even distorted 
by the embedding processes necessary before cutting with 
a microtome. This is least conspicuous in the series from 
seedlings A z , and for this reason I have figured sections from 
this series, but even in this the crumpled cell-walls are un¬ 
mistakable, particularly when compared with the tissues in 
Fig. 2, drawn from a hand-section through the same seedling. 
The behaviour of the xylem and phloem-bundles is, however, 
identical in the three seedlings examined, and the transition 
takes place in each with diagrammatic precision. 
The characteristic feature of this transition is that two 
bundles only enter the hypocotyl which passes into a root 
with tetrarch symmetry from the beginning. In the second 
type described by M. Van Tieghem ( 1 . c.) the number of 
phloem or xylem-bundles entering the hypocotyl from above 
is twice that of the corresponding bundles in the primary 
root. This is a common structure among Dicotyledons, as 
in many Crucifers, but I have not yet found it among Mono¬ 
cotyledons. The fourth scheme, of which Anemarrhena is 
the type, is the converse of this. The stem-bundles entering 
the hypocotyl are only half as many as those forming the 
primary root. 
A similar structure, but much confused by the presence 
of plumular traces in the stele of the hypocotyl, and by 
various irregularities during the transition, is found in the 
allied genera Asphodelns and Asphodeline. 
