ANALYTICAL KEY TO THE FAMILIES 



(Carried out, in some cases, to subfamilies and genera) 



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DIVISION I. PTERIDOPHYTA 



Fern-like, moss-like, rush-like, or aquatic plants without true flowers. 

 Reproduction by spores (without embryos). 



A. Floating plants with small 2-ranked leaves; sporocarps borne on 



the under side of the stem SALVINIACEAE, 50 



A. Terrestrial or submersed plants, not floating B. 



B. Stems conspicuously jointed, their nodes covered by toothed 

 sheaths; sporangia on the scales of terminal dry cone-like 

 spikes EQUISETACEAE, 51 



B. Stems without conspicuous sheathed joints C. 



C. Leaves closely imbricated or very narrow; sporangia sessile, 



axillary. 

 Stem short, corm-like; leaves elongate, awl-shape or linear, 



in a rosette ISOETACEAE, 58 



Stem elongate, creeping (sometimes underground) or branch- 

 ing ; leaves very short, crowded or imbricated. 

 Sporangia of two kinds, some containing many minute 

 spores (microspores), others bearing few (usually 3-4) 

 much larger macrospores SELAGINELLACEAE, 57 



Sporangia bearing uniform minute spores LYCOPODIACEAE, 54 



C. Leaves (fronds) not closely imbricated; if narrow, without 



axillary sporangia D. 

 D. Leaves (fronds) 4-foliolate, clover-like; sporocarps (inclosing 



the sporangia) stalked from the creeping stem MARSILEACEAE, 49 



D. Leaves (fronds) not 4-foliolate, simple or variously cleft; spo- 

 rangia not inclosed in basal sporocarps E. 

 E. Fertile fronds, or fertile portions of the fronds conspicu- 

 ously unlike the sterile F. 



F. Slender twining or climbing plant, the frond with alter- 

 nate paired and stalked palmately lobed divisions Lygodium, 46 

 F. Neither twining nor climbing G. 



G. Sterile fronds linear-filiform, tortuous; the fertile fili- 

 form, tipped by a 1-sided short (3-8 mm. long) 

 pinnate fertile portion Schizaea, 45 



G. Sterile fronds (or segments) broader H. 

 H. Sterile segment of the frond simple; the fertile a 



long-stalked simple spike OPHIOGLOSSACEAE, 47 



H. Sterile and fertile fronds or segments more or less 

 cleft I. 



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