66 HISTORY OF BRITISH FERNS. 



4, L. inundatum, Linnwus. — Leaves scattered, curved up- 



wards, linear ; spikes solitary, sessile. Plate XX. fig. 4. 



5. L. alpinum, Linnccus. — Leaves in four rows, of two 



forms, imbricate ; spikes solitary, sessile. 



Genus 2L SE LAG IN ELLA, Spring. 



1. S. B^inosa,, Pal. de Beauvais. — Leaves scattered, half- 

 spreading, lanceolate ; spikes solitary, sessile. 



IIL PEPPER-WORTS, or MARSILEACE^. 



Genus 22. ISOET ES, Li7ina;us. 



1. I. lacustris, Linnwus. — The only species. Plate XIX. 

 fig. L 



Genus 23. PILULARIA, Linnwm. 



L P. glohulifera, Linnwiis. — The only species. Plate 

 XVIL fig. 2. 



IV. HORSETAILS, or EQUISETACE^. 



Genus 24. EQUISETUM, Linnwus. 



L E. Telinateia, jC/^r/^ar^. — Stems dissimilar, the sterile 

 branched, smooth, with about thirty ridges ; sheaths 



