TAXONOMY 289 
of branching roots below and a thick rosette of long, stiff awl-shaped 
leaves above—Heterosporous. 
SUBDIVISION II.—EQUISETINE^E 
(The Horsetails or Scouring Rushes) 
The Equisetineae, commonly known as the Horsetails or Scouring 
rushes, are perennial plants with hollow, cylindrical, jointed and 
Fig. 157 .—'.Selaginella Martensii. a, vegetative branch; b, portion of the 
stem, bearing cjnes ( x ); c, longitudinal section of a cone, showing microsporangia 
( mic . sp.) in the axils of microsporophylls, and megasporangia in the axils of meg- 
asporophylls; d, microsporangium with microsporophyll; e, microspores; /, por¬ 
tion of wall of sporangium, greatly magnified; g, megaspore; h, microsporangium 
opened, and most of the microspores scattered; i, megasporangium, with mega- 
sporophyll; k, same, opened, showing the four megaspores. {Gager.) 
fluted stems, sheath-like whorls of united leaves and terminal cone¬ 
like fructifications. Their bodies contain large amounts of silicon, 
hence the name scouring rushes. 
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