12 Sargant . — Theory of the Origin of Monocotyledons 
its variations from the Anemarrhena structure are hardly less 
important. 
The existence of lateral bundles in the cotyledonary sheath 
is, as I have said, characteristic of this tribe. In Albuca 
we see a number of such lateral bundles present side by side 
with the main bundles, but obviously derived from them, and 
exercising no influence on the symmetry of the hypocotyle- 
donary stele. In other genera such lateral bundles assume 
a greater importance, and to some extent replace the main 
bundles, but these variants on the typical structure are linked 
to Albuca by a series of intermediate forms, some of which I 
shall describe in detail (. Hyacinthus romanus , Muscari atlan- 
ticum , M. armenaicum). The comparative study of these 
species and others, joined with that of a series among the 
Asphodeleae, leaves no doubt that the lateral bundles of 
the cotyledon are structures of more recent date than the 
main bundles. 
Again, the formation of a triarch root in some individuals 
of this species by the suppression of the median protoxylem 
group in one of the main bundles (A 3 , A 5 ), and the temporary 
suppression of the corresponding group in A 5 , indicates a 
tendency in these median protoxylem groups to disappear. 
Moreover, the fact that the median group which survives is 
that next to the plumular traces shows the influence that 
these — when developed early — may exercise on the symmetry 
of the stele. 
Galtonia candicans and Dipcadi serotinum are alike in 
possessing several lateral bundles in the cotyledonary sheath 
besides the two main bundles which run the whole length 
of the cotyledon. In both genera two or more of these lateral 
bundles, together with the plumular traces inserted on them, 
enter the hypocotyledonary stele, and exercise a capricious 
influence on the symmetry of the root- stele. Individuals 
within the same species differ profoundly from each other in 
the details of transition : triarch, tetrarch, or pentarch steles 
are found in the primary root of Galtonia candicans ; triarch 
or tetrarch steles in that of Dipcadi serotinum . The behaviour 
