XIII. 



Terrestrial, rarely subaquatical. Stems originating from a true, sub 

 terraneous rhizome, elongate, articulate, mostly hollow, simple or branched, 

 if branched, the branches usually placed in regular whorls at the bases 

 of the internodations, longitudinally ribbed or striated at least when 

 barren, the hollows closed over at the nodes; vascular bundles consisting 

 of several free groups of tracheide bundles placed in a circle surrounding 

 the central hollow, enclosed by a single or a double row, or an own row, 

 of endodermal cells (which are recognizable in having the connecting walls 

 provided with solitary, thickened points) O, surrounded by a circle of 

 alternate, hollow tubes (valecular canals). Leaves very small, whorled, 

 laterally connected so as to form distinct, toothed, tubular or funnel-shaped 

 sheaths enclosing the bases of the internodations of the stems and branches ; 

 sporophylla peltate, scale-like, forming terminal spikes, bearing 6 9 

 sporangia in a single row round the under side of the margin. Stomata 

 on the leaves, and generally also on the stems and branches, arranged 

 in 1 or more close lines forming 8 60 distant, longitudinal series. Spores 

 of 1 kind, globose, provided with 4 relatively very long, filiform, cruciate, 

 hygroscopic appendages (elaters) ( 2 ) which are clavate at the apex. - 

 Engl. & Prantl, Nat. Pfl.Fam., I 4 , fig. 321, 333, 343. 



Cosmopolitan. 



00. EQUISETTJM, 



Characters those of the family. 



Arrangement of the sections. 



1. HIPPOCHAETE. Stomata with their aperture immersed beneath the 

 epidermis, connected with an epidermal cavity recognizable by a 



0) Visible by ca 200 times magnifying power. Engl. & Prantl, I.e., fig. 327 A 

 (e l & e 2 ) and B (c). 



( 2 ) Stretched when dry, spirally involute when moist. Engl. & Prantl, 1. c., 

 fig. 336 A. 



