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General Keys 1. Plants woody. trees. shrubs. or subshrubs ............................................................. Key 1. xx 1. Plants herbaceous. 2. Plants free-floating on the surface (fig. 2) (in Lemna trisulca floating below the surface. lacking distinct stems and leaves. fig. 402f. g) ................................................................................ Key 2. xxiii 2. Plants submersed. emersed. terrestrial. or with floating leaves. usually rooted (fragmented specimens often free-floating). 3. Stems and leaves. or their divisions. limp. thread-like (fig. 3). or ribbon-like (fig. 5). more than 10 times as long as wide (figs. 3. 4. 5. 6) .............................................................................. Key 3. xxv 3. Stems and leaves various. but not limp and thread-like or ribbon-like. 4. Leaves compound. cut into several flat leaflets (fig. 7) .............................................. Key 4. xxxi 4. Leaves simple (sometimes pinnate-pinnatifid. fig. 25b); or stem naked or appearing naked (figs. lOa. 13). 5. Leaves deeply lobed (fig. 8b.d.e.g). or blade with basal lobes (fig. ge-k). or leaves peltate. petiole attached near center of blade (fig. 9a). 6. Leaves deeply lobed. or basal lobes extending laterally or forward (fig. 9g) ........................... Key 5. xxxiii 6. Leaves w'th basal lobes extending below junction of blade and petiole (fig. 9e-k). or leaves peltate (fig. 9a) .... , Key 6. xxxv 5. Leaves unlo1 led to shallowly lobed (leafbases sometimes cordate. but not with distinct basal lobes). never peltate; or stems naked or appearing naked. 7. Stems conspicuously jointed. with small. tooth-like leaves united in a sheath at each joint (figs. 32. 33. 34) ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Equisetaceae. 1:17 7. Stems not jointed or having tooth-like leaves united in a sheath. 8. Leaves basal or cauline. more than 10 times as long as wide; or stems naked or appearing naked. with leaves reduced to bladeless sheaths ..................................................... Key 7. xxxviii 8. Leaves basal or cauline.less than 10 times as long as wide ................................... Key 8. xlvi xix Key 1 Plants woody, trees, shrubs, or subshrubs 1. Leaves scale-like (fig. Ie) or subulate. 2. Branches bearing cones. with seeds borne on cone scales (fig. 1b). 3. Leaves scale-like, opposite; leafy twigs somewhat to strongly flattened (fig. Ie) .......................... Cupressaceae, 1:28 3. Leaves subulate, alternate; leafy twigs not flattened (Taxodium) ..................................... Taxodiaceae, 1:34 2. Branches bearing terminal spike-like racemes of true flowers, with seeds enclosed in fruits (Tamarix) ............ Tamaricaceae, 1:129 1. Leaves needle-like (fig. 1b,c) or flat and narrow to broad (fig. 1a,f,h). 4. Leaves needle-like. 5. Trees; branches bearing cones, with seeds borne on cone scales, true flowers not produced. 6. Leaves usually in clusters on spur shoots (fig. 1b), scattered on new growth of stems (Larix) ., ............... Pinaceae, 1:28 6. Leaves scattered on the twigs (fig. Ie). 7. Leaves flattened, flexible, 2-ranked (fig. 1c); stems somewhat smooth; cone scales peltate (Taxodium) ....... Taxodiaceae, 1:34 7. Leaves mostly 4-sided, stiff, spirally arranged; stems roughened with persistent peg-like petioles; cone scales attached at base (Picea) ............................................................ Pinaceae, 1:28 5. Shrubs, low, spreading, much branched; branches bearing true flowers, with seeds enclosed in black, fleshy fruits (Empetrum) ................................................................. Empetraceae, 1:153 4. Leaves flat and broad, or if narrow, then not needle-like. 8. Leaves and buds fragrant, aromatic when crushed. 9. Leaves and young stems resin-dotted; flowers borne in catkins on last year's stems; perianth absent. bracts subtending flowers brown (Myrica) ..................................................... Myricaceae, 1:72 9. Leaves and young stems lacking resin dots; flowers borne in clusters from buds on last year's stems; perianth yellow (Lindera) ................................................................... Lauraceae, 1:35 8. Leaves and buds not aromatic. 10. Leaves pinnately compound (fig. If). 11. Leaves opposite (fig. 296e). 12. Stem pith large; lenticels large, conspicuously raised; flowers bisexual, with white petals; fruit a berry-like drupe (Sambucus) .................................................... ; .. Caprifoliaceae, 1:372 12. Stem pith small; lenticels small, not conspicuously raised; flowers unisexual, lacking petals; fruit a samara. 13. Leaflets mostly 3-5, lobed or coarsely serrate; twigs glaucous (Acer negundo) . . . . . . . . . . . . . .. Aceraceae, 1:243 13. Leaflets mostly 5-11, entire or serrate; twigs not glaucous (Fraxinus) ..................... Oleaceae, 1:323 11. Leaves alternate (fig. 150a,c). 14. Stipules present, adnate to lower portion of petiole (figs. 7g, 150c); flowers pink or yellow, solitary; non-poisonous. 15. Stems prickly; flowers pink; fruit a cluster of achenes enclosed in a red hip (Rosa) ............. Rosaceae, 1:179 15. Stems not prickly; flowers yellow; fruit a cluster of achenes not enclosed in a hip (Potentilla fruticosa) Rosaceae, 1:179 14. Stipules absent; flowers cream-colored, in somewhat pendulous axillary panicles (fig. 1969); poisonous, causing dermatitis (Toxicodendron) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Anacardiaceae...

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