4(3). Plants often forming broomlike clumps; stem naked except for distantly 

 placed minute scalelike leaves; sporangia subtended by 2 minute 



scale leaves and scattered on upper part of branches 



1 . Psilotaceae, p. 37 



4. Plants not in broomlike clumps; stem with closely placed or imbricated leaves; 



sporophylls not bifid, borne in cones (5) 



5(4). Plants with erect fruiting stems; cones cylindric; spores of 1 kind 



2. Lycopodiaceae, p. 39 



5. Plants with ascending or spreading fruiting branches; cones more or less 



quadrangular; spores of 2 kinds 3. Selaginellaceae, p. 41 



6(1). Plants usually large and conspicuous, growing in soil or on rocks or trees, 

 or (if free-floating or submerged) large and dendroid; spores of 1 

 kind, minute (7) 



6. Plants small, free-floating or partially submerged or rooted in mud; spores of 



2 kinds, borne in sporocarps (10) 



7(6). Fertile fronds with 2 distinct parts, the fertile part being in the form of 

 a spike or panicle and arising from the petioles, the sterile part of 



the frond being either entire or pinnately dissected 



6. Ophioglossaceae, p, 47 



7. Fronds not as in Ophioglossaceae (8) 



8(7). Sporangia in panicles or (sometimes fingerlike) spikes developed from the 

 modified blade or parts of the blade 7. Osmundaceae, p. 51 



8. Sporangia borne on the back of (the lower side of) or on the margin of the 



blade (9) 



9(8). Plants never free-floating nor dendroid; sporangia usually long-stalked 



10. Polypodiaceae, p. 61 



9. Plants usually free-floating or very rarely deeply submerged, the sterile leaves 



forming a floating sterile rosette; sporangia sessile or nearly so 



1 1. Parkeriaceae, p. 77 



10(6). Plants rooting in mud or on muddy bottoms; rootstocks creeping; leaves 



quadrifoliolate or filiform, not imbricate nor matted, distant 



8. Marsileaceae, p. 53 



10. Plants free-floating or resting on mud; rootstocks pinnately branched; leaves 



deeply 2-lobed, imbricaite, matted 9. Salviniaceae, p. 57 



II. Gymnospermae (p. 79 of text) 



Leaves spreading in 2 ranks, usually seasonally deciduous; cones globose; cone 

 scales club-shaped, without distinct bracts, flat or peltate, with two 

 3-angled or somewhat 3-winged seeds 12. Taxodiaceae, p. 79 



III. Monocotyledoneae (p. 85 of text) 



1. Plants 1 cm. long or usualy less, thalluslike, stemless, usually floating or 

 resting on mud or some type of extraneous matter such as leaves 

 and pieces of wood 28. Lemnaceae, p. 563 



1. Plants usually larger, not with above combination of characters (2) 



19 



