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-rauked 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 POLYPODIACKAK, 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. GYMNOSPE"RMAE 



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 TAXACBAB, 62 



SUBDIVISION II. AXG1OSPERMAE 

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



CLASS 1. MONOCOTYLEDONS AE 



Stems without central pith or an nu^rf' 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 !-.aves always alternate. Parts of the flower usually in threes or 

 sixes, npver 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 



aquati.-s Without true leaves LEMNACBAK, 259 



L. Plants with ,>tenn and leaves /sometimes scale-like) M. 



