LIFE HISTORY OF THE MALE FERN 
35 
4 - Fundamental tissue, resembling the last in aspect and function. 
5. Vascular Bundles. —These are of two kinds, viz.: stem bundles 
and leaf-trace bundles. Both are of elliptical outline, as seen in 
cross section, and are embedded in the parenchyma forming the 
broad central matrix. The stem bundles are comparatively broad 
and, as viewed in longitudinal sections, form a continuous network 
with good-sized meshes, each mesh being opposite the point of in¬ 
sertion of one of the leaves (See Fig. 13). 
In transverse section these bundles are 
seen to be usually ten in number and ar¬ 
ranged in an interrupted circle within the 
fundamental tissue. The leaf-trace bun¬ 
dles are comparatively narrow and are 
observed to come off of the stem-bundles 
and pass out through the cortex into the 
leaves (fronds). When each bundle is 
examined under a high-power magnifica¬ 
tion it is seen to be composed of: (a) an 
endodermis or bundle sheath , a single layer 
of cells with yellowish walls and granular 
contents; ( b ) a pericambium or phloem 
sheath of one to three layers of delicate 
thin-walled cells, rich in protoplasm; (c) a 
phloem , a broad zone of tissue formed of 
phloem cells, with thin cellulose walls and 
protoplasmic contents, which convey sugar 
in solution from the leaves to the roots and 
broader sieve tubes which appear polygonal 
in transverse section and whose function is that of conveying soluble 
proteins in the same direction; (< d ) a xylem (wood) formed of thin- 
walled xylem cells which store food and scalariform tubes or tracheids 
which conduct crude sap (water with mineral salts in solution) from 
the roots to the leaves (fronds). Since the xylem is surrounded by the 
phloem, the fibro-vascular bundle is of the concentric type. Strictly 
speaking the endodermis and pericambium are accessory regions, sur¬ 
rounding, but not part of the bundle proper. 
Fig. 13. — A. Cylindrical 
network of vascular bundles 
in the stem of Dryopteris 
Filix-mas. B. A portion of 
the same more highly mag¬ 
nified. At L are the inter¬ 
stices over which the leaves 
are inserted; at G are 
branches (leaf trace bun¬ 
dles) passing into the leaves 
from the main vascular 
bundles. (Sayre.) 
