1904] CHRYSLER—CENTRAL CYLINDER 165 
assumes the characters seen in the adult stem. The bundles are 
collateral in all parts of the-stem. No endodermis can be distin- 
ished. 
Calloideae.—SyMPLOCARPUS FOETIDUS has already received some 
attention in JEFFREY’s preliminary studies of monocotyledons (6). 
he seedling at the age of one year consists of a spherical tuber about 
1°™ in diameter; from the upper side of this rises a conical bud with 
a cylindrical base 4™™ in diameter, from which spring several roots. 
A transverse section through the basal region of the tuber shows an 
elliptical row of collateral strands, each surrounded by an endodermis 
(fig. 4). A little higher up several bundles at one side of the ellipse 
turn outward, so that at about the middle region of the tuber the 
bundles are arranged as a horseshoe. Opposite the open part of the 
horseshoe there is frequently a swelling of the tuber, and in some 
cases this part of the tuber separates off at a slightly higher level by 
an absciss layer; this part accordingly constitutes the cotyledon, and 
the opening in the central cylinder is the cotyledonary gap. Toward 
the upper part of the tuber the separate strands approach one another, 
as is shown in fig. 5.3 At g is the cotyledonary gap; most of the vas- 
cular strands have fused laterally, producing a hollow vascular cylin- 
der with an external and internal phloeoterma (using the term in 
STRASBURGER’S sense (15, p. 310)), broken by the wide cotyledonary 
gap and by several areas where the individual bundles have not yet 
fused; through these openings the external and internal phloeotermas 
are obviously continuous. The latter may persist for some distance 
upward, finally becoming indistinguishable, or may degenerate quite 
early, and, as is seen in jig. 7, the external phloeoterma runs for a 
short distance around the edges of the cotyledonary gap, and then 
disappears. Compare jigs. 2 and 3 of Acorus, also JEFFREY’Ss figure 
of Ranunculus rhomboideus (6, fig. 16). A little higher up the cotyle- 
donary gap closes and the stele forms a hollow tube with external 
and internal phloeoterma. Almost immediately, however, the vas- 
cular tissue aggregates into separate strands, the xylem of which is 
disposed circularly (amphivasal bundles), and a few of these turn 
into the central region of the stele (fig. 6). Each of these bundles is 
surrounded by a portion of the internal phloeoterma, if this has not 
3Figs. 5, 6, 7,8, and 11 are from sections treated with sulfuric acid. 
