38 American Midland Naturalist Monograph No. 7 



17. Calyx 6-parted; stamens 9; anthers opening by 

 valves; flowers fragrant, in small clusters; twigs 

 with spicy odor and flavor 74. Lauraceae 



17. Calyx tubular, corolla-like, obscurely 4-toothed .... 

 76. Thymelaeaceae 



Section 18. Ferns and Fern- Allies (Lycosphens) 



1. Plants attached to the substratum by roots, either growing on land or sub- 

 merged in water, but not free-floating. 

 2. Leaves not quadrifoliolate or clover-like. 



3. Leaves narrow, sessile, 1 -veined, subulate or linear or oval, simple, not 

 "fern-like." 

 4. Leaves not whorled : stem solid, not conspicuously jointed. 

 5. Stems elongated, leafy. 



6. Cones terete (or in some species the sporangia borne in the axils 

 of ordinary leaves) ; spores of only one kind; leaves without a 



ligule 1. Lycopodiaceae 



6. Cones more or less 4-angled; spores of two kinds, large (mega- 

 spores), and small (microspores), borne in different sporangia 



in the same cone; ligule present 2. Selaginellaceae 



5. Stem short, thick, corm-like ; leaves rush-like, in a basal tuft; 



plants aquatic or growing in wet soil 3. Isoetaceae 



4. Leaves whorled. united to form toothed sheaths at the conspicuous 

 nodes on grooved, usually hollow stems; sporangia in a terminal 



cone 4. Equisetaceae 



3. Leaves usually broad and "fern-like" in most species, petiolate, often 

 compound, with numerous or several free (rarely netted) veins. 



7. Small delicate ferns with filmy translucent leaves usually consisting of 

 a single layer of cells; sporangia sessile on a filiform receptacle 

 within a tubular or urceolate indusium 6. Hymenophyllaceae 



7. Larger ferns with the leaves membranous to coriaceous, consisting of 

 several layers of cells; sporangia not as above. 



8. Sporangia large, sessile, opening by a transverse slit, borne in a 

 stalked terminal spike or loose panicle, the sterile blade appear- 

 ing lateral; vernation erect or inclined 5. Ophioglossaceae 



8. Sporangia small, stalked, borne in clusters (sori) on the back of 

 ordinar>- or modified foliar leaves, or in pod-like divisions of 

 modified leaves; vernation usually coiled. 



9. Sporangia covering some or all divisions of the fertile leaves, 

 densely crowded, short-stalked, globose, opening by a longi- 

 tudinal slit into two valves; annulus none; veins free 



7. Osmundaceae 



9. Sporangia in sori on the back or margin of ordinary or modified 

 leaves, long-stalked, opening by a nearly complete vertical 

 ring (annulus) 8. Polypodiaceae 



2. Leaves quadrifoliolate, clover-like, long-stalked ; sporocarps ovoid, borne 

 at the base of the stalks and containing both megaspores and micro- 

 spores; plants perennial with slender rhizomes 9. Marsileaceae 



1. Plants not attached by roots, minute (5-25 mm broad), free-floating; leaves 



imbricated, 2-lobed; sporocarps in pairs beneath the stem 



„ , ,,,..,....,...,,....,..... , 10. Salviniaceae 



