CHAPTBE XI. 



BRANCH V. PTERIDOPHYTA. 

 THE FEENWOETS. 



401. 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. 



402. Their tissues show a high degree of development. 

 The epidermis is distinct, and contains breathing-pores 

 similar 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 

 strengthening 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. 



403. The round of life of a fernwort shows an alternation 

 of generations even more marked than that of mossworts. 

 When a spore of a fernwort germinates, it pi-oduces a 

 small, flat, green, liverwort-like plant upon which sexual 

 organs arise. This is the sexual plant or gametophore. 

 After fertilization has taken place in the sexual organs a 



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