66 
HISTORY OF BRITISH FERNS. 
4. L. inundatuni, Linnwus, — Leaves scattered, curved up- 
wards, linear ; spikes solitary, sessile. Plate XX. fig. 4. 
5. L. alpinum, — Leaves in four rows, of two 
forms, imbricate ; spikes solitary, sessile. 
Genus 21. SELAGINELLA, Spring, 
1. S. spinosa, Pal, de Beauvais, — Leaves scattered, half- 
spreading, lanceolate ; spikes solitary, sessile. 
III. PEPPER-WORTS, or MARSILEAOE^. 
Genus 22. ISOETES, Linnceus, 
1. I. lacustris, Linnceus, — The only species. Plate XIX. 
fig. 1. 
Genus 23. PI LU LARI A, Linnceus. 
1. P. globiilifera, Linnceus. — The only species. Plate 
XVII. fig. 2. 
IV. HOESETAILS, or EQUISETACE.®. 
Genus U. EQUISETUM, Linnceus, 
1. E. Telmateia, — Stems dissimilar, the sterile 
branched, smooth, with about thirty ridges ; sheaths 
