334 
FERNS AND THEIR ALLIES 
Figure 304. — Cross Section of Stem 
of Pteris. 
A, epidermis; B, mechanical tissue; 
C. conductive tissue; D, fundamental 
tissue. 
The stem of the pteris 
fern is composed of well- 
defined clusters of cells 
which are grouped into 
tissues. These tissues 
are: (1) the epidermal 
on the outside, which 
protect the stem; (2) the 
fundamental, which make 
up the body of the stem 
and carry on most of the 
vital processes; (3) the 
mechanical tissues, vari¬ 
ously grouped, which by 
means of their thick-walled cells give the stem firmness; 
and (4) the conducting tissue, which is made up of several 
different kinds of cells, all of which carry liquids (Figure 304). 
The conducting tissue extends 
into the leaves and is the vein of 
the leaf. During certain seasons 
of the year, lines form along the 
margin of the under surfaces of 
the leaves. These lines are made 
up of many minute reproductive 
bodies, the sporangia (spor-an'ji-a: 
Greek, spore, seed; angeion, ves¬ 
sel). Each sporangium contains 
numerous spores. In some ferns 
the sporangia occur in dots, the 
sori (singular, sorus; Greek, soros, 
heap). (See Figures 306 and 307.) 
286. Life History of the Fern. 
— The fern plant just described 
forms spores in the sporangia. Figure 305.-Pteris, A Common 
These spores fall to the ground Fern. 
