54 HISTORY OF BRITISH FERNS. 



III. PEPPERWORTS = MARSILEA CE^. 



Flowerless plunts, hearinrf axillary or radical spore- 

 cases, having many cells. They comprise tJie genera 

 Isoetes and Pilularia. 



22. Isoetes = Stemless, quill-leaved, water plants, ■witli 



the fructifications enclosed witliin the swollen bases 

 of the leaves. 



23. Pilularia = Creeping, slender-leaved, water plants, 



with the fructifications in globular, sessile, four- 

 celled spore-cases. 



IV. HORSETAILS = EQ UISETA CEJE. 



Flowerless plants, with spore-cases attached beneath pel- 

 tate scales, iddch are arranged in terminal cones. 

 This group consists of the genus Equisetum. 



24. Equisetum = Jointed, tubular-stemmed plants, with 



terminal cones of fructification. 



