54 
HISTORY OF BRITISH FERNS. 
III. mVVm^Om& = MABSILEACEJE. 
Flowerless 'plants, hearing axillary or radical spore- 
cases, ha'cing 'many cells. They comprise the genera 
Isoetes and Pilularia. 
22. Isoetes = Stemless, quill-leaved, water plants, with 
the fructifications enclosed within 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 U I SETA CEJE. 
Flowerless plants, with spore-cases attached beneath pel- 
tate scales, which are arranged in terminal cones. 
This group consists of the genus Equisetum. 
24. Equisetum = Jointed, tubular-stemmed plants, with 
terminal cones of fructification. 
