The Flora of the Cayuga Lake Basin 15 



ARTIFICIAL KEY TO THE FAMILIES OF VASCULAR PLANTS 



PAGE 



a. Reproduction by spores in sporangia on the under side of the leaves, in the 



leaf axils, in cone-like spikes, or on short basal brandies. (Pteridophyta). 



b. Leaves (fronds) broad, flat, and fern-like, more or less pinnately or 



ternately divided or entire. 



c. Sporangia with an annulus, splitting open by a transverse cleft on one 



side, the walls 1 cell thick; fronds similar or dimorphic. .Pol ypodiaceae 26 

 c. Sporangia without an annulus, splitting open by a vertical slit; fronds 

 dimorphic or at least the fertile and sterile divisions very dissimilar. 

 d. Sporangia on special modified fronds or on much modified divisions at 

 the summit or middle of the sterile frond; walls of the sporangia 

 1 cell thick; rootstocks stout; fronds in large clumps. .Osmundaceae 33 

 d. Sporangia aggregated in spikes or panicles apparently at the summit of 

 the stem, with the leaf-like sterile part lateral or basal ; walls of the 

 sporangia several cells thick; rootstocks practically wanting; fronds 



not in clumps Ophioglossaceae 35 



b. Leaves narrow, small, and scale-like, or larger, divided, and clover-like 

 (see also 3d b). 



c. Leaves 4-foliolate, clover-like Marsileaceae 34 



c. Leaves subulate, scale-like. 



d. Leaves whorled, forming sheaths at the nodes of the jointed stem; 



sporangia in terminal spikes Equisetaceae 36 



d. Leaves not whorled; stems not conspicuously jointed. 



e. Plants aquatic, floating, small, branched, and coral-like. .Salviniaceae 34 

 c. Plants not aquatic. 

 /. Plants not resembling mosses, the stems often long and creeping ; 



spores all alike Lycopodiaceae 38 



/. Plants small and moss-like; spores of two kinds (microspores and 



megaspores) Selaginellaceae 40 



b. Leaves long and quill -like, all basal Isoetaceae 40 



a. Reproduction by seeds each containing an embryo (Spermatophyta). 



b. Ovules and seeds exposed on open bracts ; trees and shrubs, with needle- 

 like or scale-like, mostly evergreen, leaves (Gymnospermae). 



c. Seeds borne in cones or in a several-seeded berry Pinaceae 41 



c. Seeds solitary, loosely invested by a pulpy cup Taxaceae 41 



b. Ovules and seeds in a closed ovary ; herbs or woody plants, with broad or 

 narrow, evergreen or deciduous, leaves (Angiospermae). 

 c. Plants scarcely differentiated into stem and leaf ; floating aquatics. 



Lemnaceae 135 

 c. Plants ordinary, leafy. 

 (/. Ovary inferior. (2d d, p. 17.) 



e. Herbs, rarely slightly woody at base. (2d e, p. 17.) 

 /. Leaves opposite or verticillate. (2d /, p. 16.) 



g. Flowers in umbels Araliaceae 319 



g. Flowers in involucrate heads (see also 3d g) . 



h. Stamens syngenesious Compositae 394 



h. Stamens separate or but slightly united. 



i. Heads greenish or yellowish, unisexual imbrosia 413 



and Xanthium 414 

 i. Heads white, purple, or blue; flowers perfect. . .Dipsacaceae 391 

 g. Flowers neither in umbels nor in involucrate heads. 

 h. Corolla gamopetalous ; limb of calyx often minute. 



i. Leaves opposite without stipules, or if stipulate the corolla 

 rotate or saucer-shaped. 



