founded on the Structure of their Seedlings . 21 
very commonly during the transition by the characteristic 
branching of their xylem in three directions. The median 
protoxylem ray when formed is as a rule suppressed in the 
course of the transition : now and then it persists and affects 
the symmetry of the root-stele. 
Finally, in the three species Lachenalia Nelson i, Scilla 
peruviana , and Ornithogalum exscapum , lateral bundles are 
either absent from the cotyledonary sheath, or, if present, they 
take but little share in the transition. The diarch root is 
formed from the much reduced main bundles, with more or 
less assistance from the plumular traces. The transition in 
these species approaches that characteristic of such bulbous 
genera as Allium and L ilium, 
Lachenalia Nelsoni. The cotyledonary sheath contains three 
slender lateral bundles, as well as the two main bundles which 
lie side by side and have a common protoxylem group (cf. 
Eucomis nana). The lateral bundles of the cotyledon together 
with those of the plumule are all inserted on the midrib trace 
of the first leaf. The trace of the double bundle from the 
cotyledon and the single plumular trace take an equal share 
in the formation of the diarch root-stele. The plumular 
phloem divides itself between the two phloem groups of the 
cotyledon. The plumular protoxylem turns outwards. The 
group of protoxylem common to the two cotyledonary traces 
also turns outwards, and the diarch root is then complete. 
Scilla peruviana. There are no lateral bundles in the 
cotyledon. The two main bundles form a double structure as 
in Eucomis. The double trace from this enters the hypo- 
cotyledonary stele together with a single plumular trace. 
Together they form a diarch root as in Lachenalia. 
Ornithogalum exscapum. Two massive bundles run the 
whole length of the cotyledon. In the sheath they are placed 
very much as the bundles of Albuca (PI. I, Fig. 2). A single 
plumular trace takes part in the transition, but seems to 
exercise no influence on the symmetry of the stele. 
