428 PTERIDOPHYTES (FERN PLANTS) 
the structures characteristic of the stems of Seed Plants and are, 
therefore, not merely stems in appearance as the stem-like struc- 
tures developed by the gametophytes of Mosses and some Liver- 
worts are. It remained for the sporophyte generation to develop 
Fic. 379. — A Tree Fern. After Bailey. 
arealstem. At the tip of the Fern sporophyte there is a meriste- 
matic region which by the rapid growth and division of its cells 
elongates the stem. Just behind the advancing tip new roots 
and leaves are developed and stem tissues are formed. A cross 
section of a stem, as shown in Figure 380, shows an epidermis, 
cortex, vascular cylinder, and pith — tissues characteristic of 
the stems of Seed Plants. 
The roots too are true roots and are not simple structures like 
the rhizoids of gametophytes. They have a root cap, region of 
growth and elongation, epidermis, root hairs, cortex, and vascu- 
lar cylinder, thus having the features characteristic of the roots 
of Seed Plants. 
The leaves, although true leaves, are generally called fronds, 2, 
term formerly applied to them because they were considered a 
combination of leaf and stem. Fern leaves are usually much 
branched and are easily identified by the way their veins branch 
and by the way they develop in the spring. Their veins branch 
by forking; that is, a vein divides into two veins of equal size 
