CALAMOPHYTA 353 
Family 11. Polypodiaceae. Common Ferns. Spor- 
angia compressed, splitting trans- 
versely.—Polypodium, Asplenium, 
Nephrodium, Adiantum, Pteridium. 
Order MarsiuiALes. Water Ferns. Spores of two kinds; 
gametophytes dioecious, rounded. 
Family 12. Marsiliaceae. Perennial plants rooted in 
the mud, mostly bearing 4-parted 
leaves.—Marsilia, Pilularia. 
Family 13. Salviniaceae. Annual, small, floating, 
nearly rootless plants.—Azolla, Sal- 
vinia. 
Phylum X. CALAMOPHYTA. The Calamites 
Minute sexual plants (gametophytes), producing cylindrical, 
jointed and rooted sporophytes which bear 
whorled leaves. (Living species about 
24, but very many extinct.) 
Class 22. SPHENOPHYLLINEAE. Wedge-leaved Calamites. 
Paleozoic herbaceous plants of mod- 
erate dimensions and solid, jointed 
stems; long extinct. Isosporous. 
Order SPHENOPHYLLALES, including Family 1, Spheno- 
phyllaceae. 
Class 23. EQUISETINEAE. Horsetails. Paleozoic to recent 
herbaceous plants with hollow, 
jointed stems. Isosporous. 
Order EquiseTaLes. Spore-bearing cones terminal. 
Family 2. Equisetaceae. With one living genus.— 
Equisetum. 
Class 24. CALAMARINEAE. Old Calamites. Paleozoic 
plants, often trees, with hollow, in- 
creasing stems, long extinct. Hetero- 
sporous. 
Order CALAMARIALES, including Family 3, Protocalamaria- 
ceae; 4, Calamariaceae. 
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