founded on the Structure of their Seedlings. 1 1 
two massive bundles on which the transition depends (Fig. 2). 
These behave precisely as the corresponding bundles of 
Anemarrhena (Diagram VI). The phloem group of each 
divides into two parts, and the protoxylem group branches in 
three directions (px 1 ,px 2 ,px z on one side, and px^px\,px 3 on 
the other in Fig. 3, PI. I). The four phloem groups thus 
formed continue downwards into the primary root, but the 
six protoxylem groups of Fig. 3 are reduced to four by the 
fusion of px 2 with px' 2 and px z with px\. 
So far the transition follows the Anemarrhena type exactly. 
But in Albuca the permanent stele of the primary root is not 
always tetrarch. The protoxylem group px z + px\ in Fig. 4 
is less prominent than the other three. A little lower down 
it has disappeared altogether ; the phloem groups on either 
side of it have united, and the root-stele is triarch. In the seed- 
ling A 5 a similar suppression occurs. The primitive tetrarch 
structure is barely indicated before two of the protoxylem 
groups — those corresponding to px 2 4- px' 2 and px. A + px\ 
in Fig. 3 — become less prominent, and for a considerable 
distance it appears as if the root would ultimately become 
diarch. In the end, however, one of the menaced protoxylem 
groups recovers itself, and the root is triarch as in A 3 . In 
both seedlings the lateral protoxylem group which persists is 
that on the side from which the plumular traces have entered 
the stele. 
If the irregularity just described could be thought to cast 
any doubt on the homology of the transition in Albuca with 
that of Anemarrhena , that doubt would be removed by the 
series from B 1} the oldest seedling cut. In this transition the 
two cotyledonary traces give rise to a tetrarch root. The 
process is the same as in Anemarrhena , step for step, and 
when once formed the root continues tetrarch to the end 
of the series, a distance of *75 mm. from its first formation. 
The vascular structure of the seedling in Albuca Nelsoni is 
doubly interesting. In the first place it follows the Anemar- 
rhena type of transition so closely as to demonstrate the 
existence of this type within the Scilleae. In the second, 
