LIFE HISTORY OF THE MALE FERN 
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blem, originating cortex, and the plerome originating the bundle and 
related tissue. 
Continuity of Crude Sap Flow. — The crude sap (water with mineral 
salts in solution) penetiates the thin walls of the root hairs by osmosis 
and passes into the interior of hairs, thence into the root xylem and 
through this to stem xylem, thence through stem xylem into the 
leaves. 
Histology of Stipe (Petiole). — This in transverse section passing 
from periphery toward the center presents the following structural 
characteristics: 
1. Epidermis, a single layer of epidermal cells with dark brown 
outer walls. 
2. Outer cortex (hypodermis), a wide band of small cells with ligni- 
fied walls. 
3. Inner cortex, similar to inner cortex of stem but devoid of leaf- 
trace bundle. 
4. Fundamental parenchyma, similar to same region of stem in 
which are embedded a number of concentric fibro-vascular bundles 
arranged in an interrupted circle. Each of these shows a central 
xylem mass surrounded by an outer phloem mass. Each bundle is 
enveloped by a pericambium and an endodermis or bundle sheath. 
Histology of Lamina. — In transverse and surface sections the 
lamina or blade shows the following structural details: 
1. Upper epidermis of wavy- walled, slightly chlorophvlloid, flat 
upper epidermal cells devoid of stomata but with rather thick cuticle. 
2. Mesophyll of irregular shaped chlorophylloid cells containing 
abundant chloroplasts. Intercellular-air-spaces are found between 
various cells which are larger in the lower than the upper region. 
Internal glandular hairs are frequently to be discerned in many of 
these spaces. 
3. Concentric vascular bundles or laminar veins that distribute 
sap to, and carry sap from the mesophyll. These are seen to be 
embedded in the mesophyll. The xylem portion of each bundle is 
nearest to the upper surface of the leaf and so the bundles approach 
the collateral type. 
4. Endodermis, a continuous layer of mesophyll cells which sur- 
rounds each bundle and binds it in place. 
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