370 



FERNS 



itself annually. Some of these stems reach a length of 

 ten or fifteen feet. They branch out and give off many 



fine roots. Leaves, termed 

 fronds, form from the upper 

 surface of the stem and grow 

 up through the soil into the air. 

 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, variously grouped, which by 

 means of their thick- walled cells give the stem firmness ; 



Figure 395. — Pteris Stem. 



Figure 396. — Fern Frond 

 Showing Sori. 



Figure 397. — Sori Enlarged. 



and (4) the conducting tissue, which is made up of several 

 different kinds of cells, all of which carry liquids (Figure 

 395). The conducting ti«sue extends into the leaves and 



