founded on the Structure of their Seedlings . 15 
position is indicated by a break in the centre of the phloem 
crescent (cf. Figs. 7 and 8). Later on the development of the 
protoxylem ray px x (PL I, Fig. 9) completes the formation 
of a tetrarch root. 
Every step in this process can be followed in the series 
of sections from which Figs. 6-9 were drawn, and it is clear 
that the whole symmetry of the root-stele depends on the 
two main bundles M 13 M 2 , and is derived from them as in 
Albuca. The two lateral bundles L, 1 2 simply contribute 
a few xylem elements to the group px z + px 3 ', and some 
phloem elements to the two lower phloem groups. In these 
points the two other seedlings examined agree with A 5 . 
Muscari atlanticum. The apex of the cylindrical cotyledon 
(PI. II, Fig. 1) contains two bundles. A little lower down 
each of these gives off a branch. The four bundles thus 
formed run downwards through the whole length of the 
cotyledon into the sheath. No additional bundles have been 
seen in the sheath of the oldest seedling examined. Through- 
out their course the two original bundles (M 13 M 2 , in Fig. 2, 
PI. II) are larger than those derived from them. 
In seedling A 4 , from which Figs. 1-3 were drawn, the 
transition takes place very suddenly, but with diagrammatic 
clearness. In Fig. 2, PI. II, the four traces are seen to 
approach each other. As they do so the phloem group of 
each branches to right and left, and from the eight branches 
five definitive phloem groups are formed by the fusion of 
three adjacent pairs. This is very clearly seen in the single 
section which separates those drawn in Figs. 2 and 3 on 
Plate II. The lowest phloem group in Fig. 3 is formed by 
the fusion of branches from l x and 1 2 . That on the left 
hand of the lowest group is derived from the lower branch of 
M x fusing with the upper one of l x . The phloem group on 
the right of the lowest is formed from the lower branch of M 2 
and the upper one of 1 2 . The two upper phloem groups 
represent the upper branches of M x and M 2 respectively. 
The xylem groups of and M 2 each branch in three 
