TRIPHYLLUM AND ARISAEMA DRACONTIUM 41 
strands which foreshadow the bundles have already been laid down 
in the cotyledon, stem-bud and hypocotyl. Near the tip of the 
cotyledon the procambium strands branch and anastomose irregu- 
larly and therefore no definite number or arrangement of them 
can be determined, but at the base the number becomes constant 
and each strand occupies a regular position. The plan of arrange- 
ment in both species is similar. In cross section the strands mark 
out a crescent in which the largest is at the middle of the bow. In 
A. triphyllum which has regularly five strands, two lie on either 
side of the central ones, while the cotyledon of A. Dracontium 
shows the same arrangement of its five principal strands, but has 
in addition one or two smaller ones. When there are two, these 
extra strands occupy positions on either side of the large middle 
trace. When only one extra strand is retained, it invariably is at 
the right. In the tubular portion of the cotyledon, the largest 
strand is in the thickest part of the wall. The strands are com- 
posed of six or seven rows of narrow elongated cells which have 
their long axis four to six times the length of their radial, and 
parallel with the longitudinal axis of the embryo. In the stem-bud, 
procambium strands have also been differentiated. In A. Dracon- 
tum the strands in the plumule are faint and there is some varia- 
tion in the number of the procambial regions. They are never 
more numerous than three and at times only the pro-cambium 
of the future midrib has been laid down. In A. ériphyllum five 
distinct procambium regions can be distinguished in the plumule. 
Procambium strands are also present in the hypocotyl and occupy 
fully one half of its entire diameter. They are continuous with 
the procambium of the stem-bud and form at the base of the 
hypocotyl the rudimentary root stele. At the base of the hypo- 
cotyl the root-cap may be distinguished, made up of several rows 
of rather large cells which stretch across its entire base and are 
continuous at the sides with the dermatogen of the embryo. In 
the outer rows the cells are empty. Meristem tissue is to be found 
at the stem-bud and at the base of the hypocotyl where the root 
takes its origin. These cells are very small and nearly isodia- 
metric. Their nuclei are large and fill almost the entire cell. 
Parenchyma cells make up the rest of the embryo. They are two or 
three times the size of the epidermal cells and are packed with 
