Order 2 .—EQ U ISE TA C E iE .
Sporangia all alike, oblong, dehiscing down the inner face,
placed 0 -9 in a single row round the under side of the margin of
stalked peltate receptacles, which are arranged in cones at the end
of the stems. Spores v e iy numerous, free, smooth, globose, furnished
with four hygroscopic filaments, clubbed at the end, which
curl round them spirally, falling to the ground and developing
usually dioicous lobcd protliallia. Antheridia placed at the tip of
the lobes, archegonia on the fleshy upper surface near the base of
the prothallia. Rhizome wide-creeping, liypogaBOUs, articulated and
sheathed at the nodes, often branched and producing tubercles.
Stems erect, cylindrical, with a distinct central hollow, which is
closed over at the nodes, distinctly ribbed, with air-cells in their
walls beneath the ribs, the cuticle abounding in silica, distinctly
jointed at each node, and furnished with a sheath, which has as
many teeth as the stem has ribs, usually homomorphic, more
rarely more or less decidedly dimorphic (barren and fertile different),
often furnished with branches arranged in regular whorls, originating
from the base of the sheaths. Proper leaves entirely absent.
Vernation not circinate. Sjnkes obtuse or pointed.
Equisetum Linn. (The only genus.)’"
Clatis.
Subgenus E q u is e tum proper. Spikes obtuse. Stomata w i t h their
apertirre on the level of the exiidermis.
Barren and fertile stems very different, the latter vernal,
fu g a c io u s ................................................................................................Sp. 1- 2 .
Barren and fertile stems different, the latter subpersistent
and develojping small branches in whorls . . Sp. 3 -4 .
Barren and fertile stems a l i k e Sp. 5 -9 .
* For further information see Milde’s elaborate Monograph in vol. xxxii.
part 2 (1867) of Nova Acta of the Imperial Leopoldino-Caroline Academy
Natui’ic Curiosorum, which contains figures, with full dissections, of all the
known species, and an abstract of it in Milde’s ‘ Filices Europeic,’ pp. 209—249;
also Duval-Jouve’s Hist. Nat. des Equisetums de France (4to, Paris, 1864, 296
pages, 10 plates), and for the fossil-types a paper by Carruthers in Seemann's
‘ Journal of Botany,’ vol. v. (1867), p. 349, tab. 70; Newman’s ‘History of
British Ferns,’ Hooker’s ‘British Ferns,’ and the 3rd edition of ‘English
Botany,’ contain figures of all the British species.