ANALYTICAL KEY TO THE FAMILIES 



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



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 Salviniaceab, 50 



kA.. 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 Equisetackae, 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 Isoktaceae, 58 



Stem elongate, creeping (sometimes underground) or branch- 

 ing; leaves very short, crowded or imbricated. 

 Sporangia of two kiuds, 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 



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

 rangia not inclosed in basal sporocarps 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 Lygodiuin, 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-stalk('<l simi)le spike QpHioGiiOSSACEAE, 47 



H. Sterile auti ft-rtile fronds or segments more or less 

 cleft I. 



9 



