'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. I5i.3elaginella Martensii. a, vegetative branch; b, portion of the 

 stem, bearing c^nes (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. 



19 



