CALAMOPHYTA 353 



Family 11. Polypodiaceae. Common Ferns. Spor- 

 angia compressed, splitting trans- 

 versely. Polypodium, Asplenium, 

 Nephrodium, Adiantum, Pteridium. 

 Order MARSILIALES. 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- 



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. 



