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56 HISTORY OR BRITISH FERNS.
II. LYCOPODIACEÆ.
xix. L y c o p o d ium , Linnoeus.
1. L. alpinum, Linnoeus.— Leaves in four rows, appressed
; spikes solitary, sessile.
2. L. Selago, Linnoeus.— Leaves in eight rows, imbricated
on the usually erect stems ; fructifications
in the axils of leaves, not spiked. PI. XX. fig. 5.
3. L. annotinum, Linnoeus.—Leaves indistinctly fiverowed,
linear-lanceolate, patent; spikes solitary,
sessile.
4. L. olavatum, Linnoeus.—Leaves scattered, incurved,
hair-pointed; spikes two or more on a stalk.
Plate XX. fig. 6.
5. L. inundatum, Linnoeus.— Leaves scattered, curved
upwards, linear; spikes soHtary, sessile. Plate
XX. fig. 4.
6. L. selaginoides, Linnoeus.— Leaves scattered, half.
spreading, lanceolate ; spikes solitary, sessile.
III. MARSILEACEÆ.
XX. I s o e t e s , Linnoeus.
1. I. lacustris, Linnoeus.— The only species. Plate
X IX . fig. 1.
xxi. P i l u l a r i a , Linnoeus.
1. P. globulifera, Linnoeus.—PLs, only species. Plate
X VII. fig. 2.
IV. EQUISETACEÆ.
xxii. E q u i s e tu m , Linnoeus.
1. E. Telmateia, Wirhart.—Stems dissimilar, the sterile
branched, smooth, with about thirty ridges, the
fertile simple, short, with large crowded sheaths,
and subulate two-ribhed teeth. Plate XX. fig. 2.
2. E. nmbrosum, Willdenow.— Stems dissimilar, the
sterile branched, rough, with about twenty ridges,
the fertile simple, with approximate appressed
sheaths, having subulate one-ribbed teeth.
3. E. arvense, Linnoeus.— Stems dissimilar, the sterile
branched, slightly rough, with from ten to
sixteen ridges, the fertile simple, with distant,
loose sheaths, having long pointed teeth.
4. E. sylvaticum, Linnoeus.— Stems similar, with about
twelve ridges, and having loose sheaths terminating
in three or four large blunt lobes;
branches deflexed. Plate XX. fig. 3.
5. E. limosum, Linnoeus.— Stems similar, smooth, with