16 STRUCTURE AND LIFE-HISTORY OF HAY-SCENTED FERN. 
be but two layers of true cortex between endodermis and hypodermis. In 
this case the outer layer has six large cells in a circle, and the inner layer 
and hypodermis have twelve cells each. The sextant walls of the apex 
thus persist, and may even at times be traced through the endodermis and 
pericycle. Plainly this does not in any sense indicate a common origin of 
endodermis and pericycle. 
In relation to the stem, the main root originates very near the apex, in that 
layer of cells which will subsequently give rise to both endodermis and peri- 
cycle (fig. 70). The rhizogenous cell is large and cubical. By three oblique 
walls a tetrahedral initial is early cut out, and from this time onward it 
behaves just as it would in a mature root. It has no fixed position in rela- 
tion to the stem-initial. Beneath (centrad) the developing root-tissues a 
great proliferation of stem-tissue takes place. The root is thus borne half- 
way through the cortex, or farther, on a “‘pedicel’’ (figs. 59-61) while it 
is of itself digesting away the outer cortex and forming a many-layered 
cap. It finally emerges through a ragged opening in the cauline cortex 
(fig. 102). 
During the elongation of the stem the vascular tissues connecting root 
and stem are much deformed, with the following result: Tracing the 
mature root inward, its stele passes obliquely half-way through the cortex 
of the stem (fig. 102), then bends sharply backward, and fuses with the 
stem stele. The cortex, endodermis, and pericycle of both organs are 
smoothly continuous. But the root-xylem, after passing a little backward, 
turns at an acute angle forward for a short distance. Some elements 
become at once cauline, and run on forward. Others, by another sharp 
bend, turn backward in joining the xylem of the stem. Rarely a tracheid 
runs directly from the root into the stem without a double bend. Phloem 
and conjunctive parenchyma follow parallel with the xylem. The depth 
of these bends varies. In any case, those tracheids which are continuous 
from root to stem must assume very peculiar shapes (figs. 58, 61, 62). 
The bending occurs at an early stage of the development, before the cells 
become lignified (fig. 61). When a root originates from a leaf-base it 
passes out in a similar manner. A double bend occurs in the vascular 
elements, but the folds are quite shallow. 
THE STEM. 
The rhizome is slender and cylindrical and more or less branched (fig. 
3). <A piece in my collection from Bucks County, Pennsylvania, grown in 
loose loam, is 35 cm. long, with branches 15 cm. and4cm.long. Another 
rhizome from Delaware County, Pennsylvania, is 8 cm. long to a fork; one 
branch runs 23.5 cm. and forks into parts 4.5 cm. and 3 cm. long, respec- 
tively; the other branch runs 19.5 cm. to a fork, with the parts 22 cm. and 
13 cm. long. The diameter varies from 1.5 mm. to 4 mm., with a mean 
of about 3mm. When fresh the rhizomes are somewhat flexible, but the 
