LIFE HISTORY OF THE MALE FERN 55 
Bup overarched by young fronds. The opposite end is known as 
the Posrerior ExTremity and in the living plant is constantly 
decaying, as the anterior portion elongates. 
Gross STRUCTURE OF THE FronD.—Each frond consists of (1) 
a stem like portion called the St1rz or leaf stalk and (2) a green, 
expanded, leafy portion called the Lammna or blade. ‘The lamina 
is further divided into a Mipris bearing its first divisions or lobes 
which are called Pinn&. Each Pinna (sing. for pinnz) is further 
divided into secondary lobes which are called Pinnutes. If a 
pinnule be examined carefully it will be seen to possess VEINS 
which are arranged in forked fashion. ‘The under side of some 
of the pinnules will be seen to possess “fruit dots” or Sori. 
Hisrotocy or Srem (Ruizome).—Passing from periphery 
toward the center, the following structures are to be observed, 
when cross sections are examined under a microscope (see Fig. 
30): 
1. Epmermis, a protective outer covering tissue, composed of 
a single layer of brownish cells from which are given off scales. 
2. OuTER CorTEX (hypodermis), a zone ‘of several layers of 
thick-walled, lignified, fibrous cells separating the epidermis 
from the softer underlying tissue. Its main function is to sup- 
port the epidermis. 
3. INNER Cortex of several layers of more or less isodiametric 
cells (cells of nearly the same length, breadth and thickness) 
with thin cellulose walls and containing stored starch surrounded 
by a protoplasmic investment. Intercellular-air-spaces occur 
between many of the cells. This tissue is called parenchyma or 
fundamental tissue. Its cells conduct sap by osmosis and store 
food. Between the cells are to be noted intercellular-air-spaces, 
many of which contain internal glandular hairs with greenish 
contents. 
4. Prru, of parenchyma, resembling the last in aspect and 
function. 
5. VASCULAR BunpLEs.—These are elongated strands of 
water tubes and other tissues which appear in cross section as 
isolated spot-like areas. If the rhizome be cut lengthwise they 
will be observed to join each other forming an open network. 
Branch bundles come off of this network, some of which course 
