14 Sargant . — Theory of the Origin of Monocotyledons 
of forms in which the lateral bundles of the cotyledon take 
a perfectly regular share in the formation of the root-stele. 
The species Hyacinthus romanus , Muscari atlanticum , 
M. armenaicum and M. neglectum , for example, form a series 
in which the lateral traces become more and more important 
until they supply a full half of the root-stele. 
Hyacinthus romanus. In the seedling figured (A 5 , PI. I, 
Fig. 5) there are four slender lateral strands in the cotyle- 
donary sheath at an age when even the midrib is not indicated 
in the first leaf (PI. I, Fig. 6). These four strands unite in 
pairs : the two traces thus formed enter the stele just above 
the transitional region, and take some slight share in the 
process of transition from stem to root. 
The two main bundles divide exactly as in Albuca. The 
bifurcation of the phloem groups is somewhat masked by the 
early formation of a phloem girdle, but in very young seed- 
lings this is still incomplete, and there is no difficulty — when 
the series of sections from seedling A 5 is followed with care — 
in identifying the phloem group to the top or north of the 
section figured in PI. I, Fig. 7 with half the phloem of M 2 . 
The rest has united with the adjacent phloem group of the 
lateral bundle 1 2 to form the right-hand or eastern group. 
The whole of the phloem belonging to has joined that 
of lj, and the united groups are now represented by the 
phloem crescent on the left hand or south-western side of the 
stele (Pl. I, Fig. 7). The xylem is in two masses, between 
which extends a slender crescent of protoxylem elements. 
This is formed by the xylem of the two lateral bundles l x and 
1 2 , together with protoxylem elements from the two main 
bundles M 1 and M 2 . These will together form the protoxylem 
group px 3 + px' 3 of figures 8 and 9 on the same plate. The 
corresponding group to the north of the stele in Fig. 8 is 
formed by the union of protoxylem branches from the two 
xylem masses shown in Fig. 7 (PI. I, Fig. 8, px 2 + p%'<f 
The median protoxylem group of M 2 ( px 4 in Fig. 8) is also 
well developed, but that of Mj can hardly be made out. Its 
