Internal Phloem in Gelsemium sempervirens, Ait. 49 
each other, thus, —< >—, but as the hypocotyl increases 
in age, the cells of the arms move apart, taking a lateral posi- 
tion, with the phloem external to them, usually two patches to 
each side. This is illustrated in Plate IX, Fig. 4. 
As differentiation proceeds more spiral trachez are inter- 
polated between those already formed, so that a continuous 
ring of protoxylem is finally present. The phloem consists 
of small patches of finely divided cells, along the outer margin 
of the sides of the wood, but is not yet continued around the 
ends. At the level of the cotyledons, the phloem from the 
sides bends toward the ends, and the zone is thus completed. 
No recognizable internal phloem could be distinguished in the 
young hypocotyl. 
In an older hypocotyl, in which secondary growth has 
gone on for some time, the fundaments of two internal phloem 
patches may be observed just below the cotyledonary node. 
The round hypocotyl becomes elliptical, preparatory to the 
separation of the cotyledons. Five or six large embryonic 
cells appear on the inner side of the wood. Their nuclei are 
large, and take a darker stain than the adjoining cells. In 
short, the fundament of an internal phloem patch has arisen 
in the leaf trace bundles, destined for the first, third, fifth and 
succeeding pairs of leaves. No such fundament is demonstra- 
ble in the pair of bundles for the cotyledons, second, fourth 
and succeeding pairs of leaves. With increased age these 
embryonic cells become a mass of small, finely divided cells, 
so that evidently the bundles for the odd pairs of leaves each 
possess an internal phloem patch. Throughout the lower 
and middle portions of the epicotyl, or the internode above 
the cotyledons, the opposite bundles are devoid of internal 
phloem, but just below the node bearing the first pair of leaves, 
two groups of embryonic cells appear in them, representing 
the fundaments of the internal phloem patches for the even 
pairs of leaves. When the node bearing the second pair of 
leaves is reached, all four patches of internal phloem are 
4 
