172 BOTANICAL GAZETTE [sepreiee 
phloeoterma is present and is not broken by the exit of a large strand 
of vascular tissue to the cotyledon. Fig. 18 shows the appearance of 
the stele in the first internode, and illustrates the tendency which the 
stele has to break up into separate strands. The three traces of the 
second leaf arise in the same manner as the cotyledonary trace; above 
this level, however, some of the strands become concentric, and one 
or two branches are given off into the pith, where they run only a 
short distance, join bundles of the vascular ring, and then pass out 
to leaves. Fig. 19 shows such a strand at m, and also a leaf trace (i) 
which is just leaving the vascular ring. Higher up other medullary 
strands run for a greater distance in the pith and turn outward to 
leaves without anastomosing with bundles of the vascular ring. The 
seedling of this plant shows clearly the gradual appearance of mono- 
cotyledonous characters in a central cylinder which in its first formed 
part closely resembles that of a dicotyledon. The mature stem both 
in its subterranean and aerial regions differs from the rhizome of 
Maianthemum in having a number of medullary strands. 
SMILACINA RACEMOSA.—In the youngest plants obtainable the 
central cylinder exhibited the characters of the adult stem, that is the 
bundles are scattered through the medulla. Seeds of this plant 
failed to sprout. : 
Smilacina stellata in that it consists of a ring of collateral bundles 
surrounded by a phloeoterma and enclosing pith; but the bundles 
early become concentric and afterwards some of them run in the 
medulla. Bundles of the vascular ring turn outward as leaf traces | 
. Hoa « 
without destroying the continuity of the phloeoterma. “ 
Potyconatum Birtorum and P. vERTICILLATUM.—The central | 
cylinder, at first a solid mass, becomes divided into about six widely 
separated collateral strands at a comparatively young stage; Mae 
n 
several medullary bundles appear; a phloeoterma is not distingws 
able. The wide separation of the strands is probably due to the fact q | 
that the subterranean stem (a horizontal rhizome) early bea a 
closes the stele becomes divided into six or eight meristeles arranged 4 
swollen into ovoid form through deposition of starch. - 
MEDEOLA VIRGINIANA.—The cotyledonary gap is wide; 4 
circularly, each provided with its own endodermis and having # 
| 
STREPTOPUS ROSEUS.—The stele of the seedling resembles that of 
