CHAPTER XII 
BRANCH VI. PTERIDOPHYTA, 
THE FERNWORTS. 
403. The Fernworts are for the most part leafy-stemmed, 
root-bearing plants of considerable size, whose leaves bear 
spores. All are chlorophyll-bearing, and they are mostly 
terrestrial in habit, comparatively few being aquatic. 
404, Their tissues show a high degree of development. 
The epidermis is distinct, and contains breathing-pores sim- 
ilar in form and position to those of the flowering plants. 
The fibro-vascular bundles are generally of the concentric 
type, although collateral and radial bundles occur also. 
The bundles generally possess tracheary and sieve tissues; 
the former is usually well developed, but the latter not. 
Fibrous tissue occurs only to a limited extent within the 
bundles, but it is common in the stems as thick strength- 
ening masses. These tissues generally develop from a 
single cell at the apex of the stem, but in the higher orders 
there are groups of apical cells, as in the flowering plants. 
405. The round of life of a fernwort shows a curious al- 
ternation of generations. When a spore of a fernwort 
germinates, it produces a small, flat, green liverwort-like 
plant upon which sexual organs arise. This is the first 
stage, or sexual generation. After fertilization has taken 
place in the sexual organs, a leafy-stemmed, long-lived 
plant is produced directly. This is the second stage, or 
