SPOROPHYTE. 13 
walls are brownish-yellow, like those of all of the cells outside of the 
endodermis. The subjacent hypodermal cells are about three times as 
wide and twice as deep radially as those of the epidermis, and similarly 
elongated. The first cortical layer is composed of cells nearly twice as 
large in cross-section as the foregoing, but like the last in length and 
character of wall. Intercellular spaces occur rarely at the angles of these 
cells. The cells of the second cortical layer are smaller again, often as 
narrow-as the epidermal cells. The two innermost layers are still smaller. 
In the last three layers, especially the middle one, thickening of the walls 
begins even before the root hairs are fully mature (fig. 43). At this stage 
the endodermal cells are already very long, narrow, and practically empty. 
Pericycle and conjunctive parenchyma are full of dense, granular contents. 
They are probably multinucleate, since the cells are very narrow and long, 
but nearly always show a nucleusin cross-sections. The pericycle cells are 
often much larger in the region of the protophloem than elsewhere (fig. 
35). The protophloems have already passed their greatest density and 
prominence and the sieve-tubes now appear mature. Each protoxylem 
consists of one or two extremely slender spiral elements, with one or two 
slightly wider scalariform tracheids on either side. The two or four large 
central tracheids of the metaxylem show as yet no thickening of the walls 
(figs. 34, 35, 36, 43, 44). 
TABLE 4.—Statistics of transverse section of root. 
No. of cells in— Cortex. No. of cells in— 
7 No. of No. of cells | No. of cells 3 
Epiderm. |Hypoderm. layers. in outer ininner |Endoderm.| Pericycle. 
layer. layer. 
64 30 4 ¥*22 20 19 21 
49 19 4 14 24 18 20 
40 iv 4 ia ie ‘ek ke 
4o 20 4 14 23 16 17 
46 26 tas *18 13 10 13 
t61 27 vs 22 20 15 19 
t52 28 40Fr 5 ae 21 15 20 
t50 26 3 21 17 13 16 
rwith 3 
14 with 4 
to with 5 
3 with 6 
*Immature. {Sections of one root, 16 4 apart. 
Following all these parts upward in an old root, we find that the epider- 
mis and outer soft layer of cortex wither after the root-hairs die, and are 
ultimately sloughed off (fig. 46). The bundle is now protected by the 
two or three inner cortical layers, whose walls have thickened so as almost 
to obliterate the lumen. Lignification in the metaxylem takes place slowly. 
In a section showing a withering epidermis, and the inner cortex indurated 
