LIFE HISTORY OF THE MALE FERN 
15 
store food. Between the cells are to be noted intercellular air spaces, 
many of which contain internal glandular hairs. 
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 and are em- 
bedded in the parenchyma forming the broad central matrix. The 
stem bundles are comparatively broad and form a continuous net- 
work with good-sized meshes, each mesh being opposite the point of 
insertion of one of the leaves. Tn transverse section these bundles 
are seen to be usually ten in number and arranged in an interrupted 
circle within the fundamental tissue. The leaf-trace bundles 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 magnification 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 proto- 
plasmic contents, which convey sugar in solution from the leaves 
to the roots and broader sieve tubes which appear polygonal in trans- 
verse section and whose function is that of conveying soluble pro- 
teins in the same direction; (d) a xylem (wood) formed of thin-walled 
xylem cells which store food and scalariform tubes or tracheids which 
copduct 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. 
Histology of Growing Apex. — When the bases of the leaves of the 
current year, the circinate leaves of the following year and the large 
mass of brown scales have been removed from around the apical bud 
of a well-grown plant, the following structures may readily be ob- 
served with a hand lens: 
1. The apical cone ( punctum vegetationis) , a rounded papilla, which 
occupies a terminal position in the apical region. 
2. The young fronds, arranged around the apical cone. 
