TAXONOMY 
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Family II. — Selaginellaceae, including the single genus Selaginella, 
with species for the greater part tropical. Plants similar in habit to 
the Lycopodiaceae but showing heterospory. 
Family III. — Isoetaceae, including the single genus Isoetes whose 
species are plants with short and tuberous stems giving rise to a tuft 
of branching roots below and a thick rosette of long, stiff awl-shaped 
leaves above — Heterosporous. 
Fig. 112. — Lycopodium clavatum. (Gager.) 
SUBDIVISION II.— EQUISETINEiE 
(The Horsetails or Scouring Rushes) 
The Equisetineae, commonly known as the Horsetails or Scouring 
rushes, are perennial plants with hollow, cylindrical, jointed and 
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. 
In some varieties the fruiting cone is borne on the ordinary stem, in 
