342 BOTANICAL GAZETTE [NOVEMBER 
When the endosperm has been exhausted, the elongation of the 
descending axis ceases. The zone of elongation in the cotyledon 
is now located near the upper end of the cotyledon, so that the 
tip of the cotyledon is withdrawn from the empty testa, and 
elevated into the light, much as in Allium (Sacus 18). From the 
haustorial cells at the tip of the cotyledon two vascular bundles 
extend downward to the base of the root, just below the level of 
the stem apex, as in Tulipa (Inwiscu 11). In some species (E. 
grandiflorum, and E. Hartwegii) there are three cotyledonary 
bundles (SaRGANT 19). After reaching the light, the cotyledon 
attains a total length of 8-10 cm. above the soil line (text fig. 6), 
and the elbow formed in the withdrawal from the seed coats 
gradually straightens. The cotyledon is cylindrical below, but may 
be considerably flattened in the upper portions, the two bundles 
lying side by side (figs. 4, 5) 
The apical dome becomes differentiated during the descent of 
the stem apex, and the cavity in which it is inclosed changes into 
a curved pocket by the elongation of the walls of the cavity (figs. 
6-10). The apex then rises as a dome from the bottom of the 
pocket. The space about the apex has a depth about equal to 
its width when the descending axis comes to rest. The thickness 
of the walls decreases from the axial to the opposite side, which 
lies immediately below the opening from the interior of the cavity 
to the exterior. The base of the cotyledon thus comes to form a 
sheath about the stem apex. The radicle has as yet grown but 
little; soon, however, the primary root is organized and advances 
from the end of the descending axis (text fig. 1). The primary 
root is the only one in the life cycle which responds positively to 
gravitation. At the base of the root a considerable cushion is 
formed, upon which root hairs are produced abundantly. By the 
growth of adjacent tissues the base of the root becomes oblique, 
and seems to be fused to the side of the cotyledonary sheath for 
a short distance (figs. 6-9). The stem apex, or plumule, has, So 
far no vascular supply from the rest of the seedling, the cells below 
the apical dome being meristematic and undifferentiated as yet 
into tissues. The plumular trace is inserted upon each of the two 
cotyledonary bundles, just before they unite to form the root 
