ANALYTICAL KEY TO THE FAMILIES* 



DIVISION I. PTERIDOPHYTES 



Fern-like, moss-like, or rush-like vascular plants without true flowers or 

 seeds. 



Stems conspicuously jointed, their nodes covered by toothed sheaths; 



sporangia on the scales of terminal dry cone-like spikes 4. EQUISETACEAE, 23 

 Stems without conspicuously sheathed joints. 



Leaves closely imbricated or very narrow; sporangia sessile, 



axillary. 



Stem short, corm-like; leaves subulate to long-linear 5. ISOETACEAE, 24 



Stems elongated, creeping or branching; leaves very short, 



crowded or imbricated. 



Sporangia of two kinds, some containing many minute spores 

 (microspores), others bearing few (usually 34) much 

 larger spores (megaspores) 7. SELAGINELLACEAE, 27 



Sporangia bearing uniform minute spores 6. LYCOPODIACEAE, 25 



Leaves (fronds) not closely imbricated; if narrow without axillary 



sporangia. 

 Leaves (fronds) 4-foliate, sporocarps (inclosing the sporangia) 



stalked from the creeping stem 3. MARSILEACEAE, 23 



Leaves (fronds) not 4-foliate, simple or variously cleft; sporangia 

 borne on the underside of the ordinary fronds (leaves) or 

 on sporophylls (specialized spore-bearing leaves). 

 Sterile segment of the frond simple; the fertile a long-stalked 



simple spike 1. OPHIOGLOSSACEAE, 17 



Sterile and fertile fronds or segments more or less cleft, either 



conspicuously unlike or essentially similar 2. POLYPODIACEAE, 18 



DIVISION II. SPERMATOPHYTES 

 Plants with seeds and mostly true flowers. 



SUBDIVISION I. GYMNOSPERMS 



Ovules not in a closed ovary. Trees and shrubs with needle-shaped, linear, 

 or scale-like leaves (mostly evergreen), and monoecious or dioecious cones. 



Staminate and pistillate cones with no true flowers (perianth none), 



the pistillate becoming dry or berry-like 8. PINACEAE, 26 



Staminate flowers in aments; pistillate single or in pairs; perianth 

 urn-shaped; low shrubs with jointed branches, and leaves re- 

 duced to sheathing scales 9. GNETACEAE, 30 



* Adapted from Gray's New Manual of Botany, as revised by Dr. B. L. Robinson and 

 Professor M. L. Fernald. 



