10 ANALYTICAL KEY 



I. Rootstock almost none, the solitary (rarely 2) fronds appear- 

 ing to rise from a cluster of fleshy roots ; lower segment 

 sterile, upper fertile and bearing 2-rowed globular 

 sporangia Botrychium, 47 



I. Rootstock well developed, elongate or stout, the roots 

 fibrous; fronds numerous or the fertile and sterile 

 clearly distinct J. 

 J. Fertile fronds or segments scarcely or not at all leaf-like, 



the sporangia globose or in bead-like rows. 

 Sporangia globose, thin-walled, 2-valved, densely 



crowded, not 2-ranked OSMUNDACEAE, 46 



Sporangia globose and distinct or connected in bead- 

 like chains, firm, 2-ranked Onoclea, 45 

 J. Fertile fronds or segments green and leaf-like, at least 



above; the sporangia not globose POLYPODIACEAE, 33 



E. Fertile fronds or segments essentially like the sterile. 



Sporangia sessile at the base of a bristle-like receptacle and 

 surrounded by a cup-like involucre ; frond of a single layer 

 of cells HYMENOPHYLLACEAE, 33 



Sporangia stalked, with no bristle-like receptacle; frond of 



more than one layer of cells POLYPODIACEAE, 33 



DIVISION II. SPERMATOPHYTA 



Plants with true flowers containing stamens, pistils, or both. Reproduc- 

 tion normally by seeds containing an embryo. 



SUBDIVISION I. GYMNOSPERMAE 



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

 or scale-like mostly evergreen leaves, and monoecious or dioecious flowers K. 



K. Flowers themselves catkin-like or borne in catkins, which be- 

 come cones or berry-like PINACEAE, 62 



K. Flowers solitary, axillary ; seed solitary, more or less enveloped 



in a pulpy disk TAXACEAE, 62 



SUBDIVISION II. ANG1OSP&RMAE 



Ovules borne in a closed ovary, which at maturity becomes the fruit. 



CLASS 1. MONOCOTYLEDONEAE 



Stems without central pith or annular layers, but having the woody fibers 

 distributed through them (a transverse slice showing the fibers as dots scat- 

 tered through the cellular tissue). Embryo with a single cotyledon, the 

 early leaves always alternate. Parts of the flower usually in threes or 

 sixes, never in fives. Leaves mostly parallel- veined. Our species, except 

 in the genus Smilax, herbaceous L. 



L. Small lens-shaped, ellipsoidal, or flask-shaped free-swimming 



aquatics without true leaves LEMNACEAE, 259 



L. Plants with stems and leaves .(sometimes scale-like) M. 



