All dimensions are expressed in the metric system. For convenience, it may be stated that 25 millimeters (mm.) are about equal to one inch; 1 centimeter (cm.) to two-fifths of an inch; 1 decimeter (dm.) to 4 inches; and 1 meter (m.) is a little more than 3 feet.

KEY TO GROUPS

1a. Trees, shrubs, or woody climbers, with stems which last from year to year[Group 1, WOODY PLANTS], p. ix
1b. Herbaceous plants, with stems which live above ground only a single season [— 2.]
2a. Plants with unusual habits or structures, including leafless, colorless, submerged, floating, parasitic, or hollow-leaved plants[Group 2, UNUSUAL PLANTS], p. xxiii.
2b. Ordinary terrestrial or swamp plants, without unusual structural peculiarities [— 3.]
3a. Leaves parallel-veined (or net-veined in a few species); parts of the flower usually in threes or sixes, never in fives; wood-fibers scattered through the stem; seed with one cotyledon. All plants with definitely parallel-veined leaves may be identified through this division, unless the parts of the flower are distinctly in fives.[Group 3, MONOCOTYLEDONES],
p. xxvii.
3b. Leaves net-veined (or parallel-veined in a few species); parts of the flower usually in fours or fives; wood-fibers arranged in a circle in the stem; seeds with two cotyledons. All plants with definitely net-veined leaves may be identified through this division.[Group 4, DICOTYLEDONES],
p. xxx.

Note:—In order to avoid possible chances of error, many plants have been treated under both of the above groups. The following hints may also be useful in distinguishing Groups 3 and 4:

All herbaceous plants with deeply lobed, dissected or compound leaves may be sought under the Dicotyledones.

All herbaceous plants with five stamens in each flower, or with seven or more stamens and one ovary in each flower, may be sought under Dicotyledones.

GROUP 1, WOODY PLANTS

1a. Trees, with erect stem and central trunk, attaining a height of 6 m. (20 ft.) or more [— 2.]
1b. Shrubs or woody vines, without true tree habit, or attaining heights of less than 6 m. (20 ft.) [— 52.]
2a. Key for use in earliest spring, for trees which have flowers but no leaves [— 3.]
2b. Key for use with trees bearing leaves [— 21.]
3a. Flowers in catkins, without brightly colored or petal-like parts [— 4.]
3b. Flowers not in catkins, either with or without petals [— 14.]
4a. Leaf-scars and lateral buds 2-ranked, i. e., in two longitudinal rows with the third leaf above the first [— 5.]
4b. Leaf-scars and buds in three or more longitudinal rows [— 9.]
5a. From 1 to 3 bud-scales visible on each leaf-bud[2b, in FAGACEAE], p. 22.
5b. From 4 to 7 bud-scales visible on each leaf-bud [— 6.]
5c. From 8 to 20 bud-scales visible on each leaf-bud; buds long and slender; bark of the trunk smooth [— 8.]
6a. Bundle-scars 5 or more[2b, in URTICACEAE], p. 23.
6b. Bundle-scars 3 [— 7.]
7a. Twigs bearing numerous dwarf branches thickly covered with crowded leaf-scars (Birch)[BETULACEAE], p. 21.
7b. Twigs without dwarf branches (Ironwood)[9a, in BETULACEAE], p. 22.
8a. Trunk cylindrical or nearly so[2a, in FAGACEAE], p. 22.
8b. Trunk prominently fluted with longitudinal ridges[1b, in BETULACEAE], p. 21.
9a. Bundle-scars 3 in each leaf-scar [— 10.]
9b. Bundle scars more than 3 in each leaf-scar [— 12.]
10a. Pith divided into separate cavities by transverse partitions[1a, in JUGLANDACEAE], p. 21.
10b. Pith not partitioned [— 11.]
11a. Buds small, with only one external bud-scale[1b, in SALICACEAE], p. 19.
11b. Buds with more than one outer bud-scale[1a, in SALICACEAE], p. 19.
12a. Buds clustered near the tips of the twigs[1b, in FAGACEAE], p. 22.
12b. Buds not clustered at the tips of the twigs [— 13.]
13a. Buds with about 3 visible bud-scales[2b, in FAGACEAE], p. 22.
13b. Terminal bud large, with 4 or more visible bud-scales[1b, in JUGLANDACEAE], p. 21.
14a. Flowers conspicuous, brightly colored, at least 8 mm. wide. with both calyx and corolla [— 15.]
14b. Flowers inconspicuous, seldom brightly colored, and then less than 8 mm. wide [— 17.]
15a. Flowers irregular, pink or red[3a, in LEGUMINOSAE], p. 58.
15b. Flowers regular, white [— 16.]
16a. Ovary one, superior, in the center of the flower[32b, in ROSACEAE], p. 54.
16b. Ovary inferior, appearing as a swelling below the calyx at the summit of the pedicel[42b, in ROSACEAE], p. 55.
17a. Leaf-scars and buds opposite [— 18.]
17b. Leaf-scars and buds alternate [— 19.]
18a. Bundle-scar one in each leaf-scar[1b, in OLEACAE], p. 88.
18b. Bundle-scars 3 or more in each leaf-scar[ACERACEAE], p. 70.
19a. Bundle-scar 1 in each leaf-scar[1b, in LAURACEAE], p. 41.
19b. Bundle-scars 3 in each leaf-scar [— 20.]
19c. Bundle-scars 5 in each leaf-scar[7a, in LEGUMINOSAE], p. 58.
20a. Branches thorny[5a, in LEGUMINOSAE], p. 58.
20b. Branches not thorny[3a, in URTICACEAE], p. 24.
— 21—
21a. Leaves narrow, needle-like or scale-like; trees mostly evergreen[PINACEAE], p. 1.
21b. Leaves broader, flat, never needle-like or scale-like, falling in winter [— 22.]
22a. Leaves compound [— 23.]
22b. Leaves simple [— 29.]
23a. Leaves opposite [— 24.]
23b. Leaves alternate [— 26.]
24a. Leaves palmately compound with 5-7 leaflets[SAPINDACEAE], p. 70.
24b. Leaves pinnately compound [— 25.]
25a. Leaflets 3-5[1a, in ACERACEAE], p. 70.
25b. Leaflets 7-11[1b, in OLEACEAE], p. 88.
26a. Stem or branches thorny[4a, in LEGUMINOSAE], p. 58.
26b. Stem or branches not thorny [— 27.]
27a. Leaflets entire[7a, in LEGUMINOSAE], p. 58.
27b. Leaflets entire except for a few large glandular teeth near their base[SIMARUBACEAE], p. 65.
27c. Leaflets serrate their entire length [— 28.]
28a. Upper leaflets less than 25 mm. wide[4b, in ROSACEAE], p. 51.
28b. Upper leaflets more than 25 mm. wide[JUGLANDACEAE], p. 21.
29a. Leaves opposite [— 30.]
29b. Leaves alternate [— 32.]
30a. Leaves entire[CORNACEAE], p. 83.
30b. Leaves toothed or lobed, not entire [— 31.]
31a. Leaves lobed[1b, in ACERACEAE], p. 70.
31b. Leaves merely toothed[27b, in CAPRIFOLIACEAE], p. 111.
32a. Leaves entire [— 33.]
32b. Leaves toothed [— 36.]
32c. Leaves lobed [— 47.]
33a. Leaves heart-shape[3a, in LEGUMINOSAE], p. 58.
33b. Leaves not heart-shape [— 34.]
34a. Twigs and foliage spicy-aromatic[1b, in LAURACEAE], p. 41.
34b. Twigs and foliage not aromatic [— 35.]
35a. Pith 5-angled; fruit an acorn[3a, in FAGACEAE], p. 22.
35b. Pith not 5-angled; fruit a berry[1a, in CORNACEAE], p. 83.
36a. Leaves oblique at base, i. e., one side of the leaf larger than the other [— 37.]
36b. Leaves symmetrical, not oblique at base [— 38.]
37a. Leaves heart-shape, about as broad as long[TILIACEAE], p. 72.
37b. Leaves oval or ovate, much longer than wide[1a, in URTICACEAE], p. 23.
38a. Stems thorny[41b, in ROSACEAE], p. 54.
38b. Stems not thorny [— 39.]
39a. Leaves finely toothed, with 3-many teeth per centimeter of margin [— 40.]
39b. Leaves coarsely toothed, with 1-2 teeth per centimeter of margin [— 46.]
40a. Petioles laterally compressed[2a, in SALICACEAE], p. 19.
40b. Petioles not compressed [— 41.]
41a. Leaves, or many of them, crowded on short spur-like branches [— 42.]
41b. Leaves scattered, not on short spur-like branches [— 43.]
42a. Bark of the trunks separating in thin papery or leathery sheets[BETULACEAE], p. 21.
42b. Bark of the trunk not papery or leathery[24b, in ROSACEAE], p. 53.
43a. Lateral leaf-veins straight and parallel, and terminating in the teeth[BETULACEAE], p. 21.
43b. Lateral veins more or less curved, and not ending in the teeth [— 44.]
44a. Leaves palmately veined, about as broad as long; juice somewhat milky[2b, in URTICACEAE], p. 23.
44b. Leaves pinnately veined; juice not milky [— 45.]
45a. Willows, with slender leaves and brittle twigs[8a, in SALICACEAE], p. 19.
45b. Trees with lanceolate, ovate, or oblong leaves and tough twigs[30, in ROSACEAE], p. 54.
45c. Cottonwoods, with broad, heart-shape or rounded leaves[1a, in SALICACEAE], p. 19.
46a. Petioles laterally compressed[2a, in SALICACEAE], p. 19.
46b. Petioles not compressed; lateral veins straight and parallel, running directly to the teeth[FAGACEAE], p. 22.
47a. Stem thorny[41b, in ROSACEAE], p. 54.
47b. Stem not thorny [— 48.]
48a. Leaves palmately veined [— 49.]
48b. Leaves pinnately veined [— 51.]
49a. Lobes of the leaf entire[1b, in LAURACEAE], p. 41.
49b. Lobes of the leaf serrate [— 50.]
50a.Juice somewhat milky; lateral buds visible[2b, in URTICACEAE], p. 23.
50b.Juice not milky; lateral buds covered by the base of the petiole[PLATANACEAE], p. 51.
51a. Leaves with 4 large entire lobes; stem marked with a ring at each node[MAGNOLIACEAE], p. 40.
51b. Leaves with many lobes; stem not ringed[1b, in FAGACEAE], p. 22.
— 52—
52a.For specimens bearing leaves only [— 53.]
52b. For specimens bearing flowers only [— 140.]
52c.For specimens with both leaves and flowers [— 155.]
53a. Leaves narrow, needle-like or scale-like, mostly evergreen [— 54.]
53b. Leaves broader, flat or rolled, but not needle-like or scale-like [— 56.]
54a. Foliage densely gray-pubescent; low bushy shrubs with yellow flowers[2a, in CISTACEAE], p. 74.
54b.Foliage green [— 55.]
55a. Leaves opposite or whorled[PINACEAE], p. 1.
55b. Leaves scattered on the stem[TAXACEAE], p. 2.
56a.Twining or climbing vines [— 57.]
56b. Not climbing or twining [— 66.]
57a. Thorny vines [— 58.]
57b. Not thorny [— 60.]
58a.Climbing by tendrils at the base of the leaves[4b, in LILIACEAE], p. 11.
58b.Tendrils none [— 59.]
59a. Leaves simple[5a, in SOLANACEAE], p. 100.
59b. Leaves compound[8a, in ROSACEAE], p. 52.
60a.Leaves compound [— 61.]
60b.Leaves simple [— 63.]
61a. Leaves with 5 leaflets[1a, in VITACEAE], p. 71.
61b. Leaves with 3 leaflets [— 62.]
62a. Plant climbing by tendril-like leaf-stalks[1a, in RANUNCULACEAE], p. 35.
62b. Plant climbing by hold-fast roots[5b, in ANACARDIACEAE], p. 69.
63a. Leaves opposite[5a, in CAPRIFOLIACEAE], p. 110.
63b. Leaves alternate [— 64.]
64a. Plants climbing by tendrils[1b, in VITACEAE], p. 71.
64b. Twining plants [— 65.]
65a. Leaves ovate-oblong, attached by the base[1a, in CELASTRACEAE], p. 69.
65b. Leaves almost round, peltate near the edge[MENISPERMACEAE] p. 40.
66a. Leaves opposite [— 67.]
66b. Leaves alternate [— 84.]
67a. Leaves compound [— 68.]
67b. Leaves simple [— 69.]
68a. Leaflets 3[STAPHYLEACEAE], p. 69.
68b. Leaflets 7 or more[1a, in CAPRIFOLIACEAE], p. 109.
69a. Leaves palmately veined, or at least with a pair of prominent lateral veins from the base [— 70.]
69b. Leaves pinnately veined [— 72.]
70a. Leaves not lobed[1b, in RHAMNACEAE], p. 71.
70b. Leaves more or less lobed [— 71.]
71a. Leaves with stipules[22a, in CAPRIFOLIACEAE], p. 111.
71b. Leaves without stipules[2a, in ACERACEAE], p. 70.
72a. Leaves serrate [— 73.]
72b. Leaves entire [— 77.]
73a. Stem thorny[1b, in RHAMNACEAE], p. 71.
73b. Stem not thorny [— 74.]
74a. Bark of the ripe twigs green[1b, in CELASTRACEAE], p. 69.
74b. Bark of the ripe twigs brown, reddish, or gray [— 75.]
75a. Twigs with a prominent hairy ridge extending downward from the middle of the line connecting the petiole bases[13a, in CAPRIFOLIACEAE], p. 110.
75b. Twigs without any pubescent ridge [— 76.]
76a. Erect shrubs; leaves obviously toothed[11b, in CAPRIFOLIACEAE], p. 110.
76b. Spreading shrubs; most of the leaves entire, and only here and there some with serrate margins[18b, in CAPRIFOLIACEAE], p. 110.
77a. Leaves silvery beneath with a dense coating of scales[ELAEAGNACEAE], p. 77.
77b. Leaves green beneath, or somewhat hairy and light-colored [— 78.]
78a. Aquatic plant with lanceolate leaves, and stems bending over and into the water[1a, in LYTHRACEAE], p. 77.
78b. Not truly aquatic, although frequently in wet places [— 79.]
79a. Leaves evergreen, as shown by their presence on the older stems[18a, in ERICACEAE], p. 85.
79b. Leaves deciduous each year [— 80.]
80a. Leaves dotted with translucent dots, easily seen when the leaf is held to the light[1a, in HYPERICACEAE], p. 73.
80b. Leaves not dotted with translucent dots [— 81.]
81a. Lateral veins curved forward and running almost parallel to the leaf-margin[CORNACEAE], p. 83.
81b. Lateral veins spreading, and not paralleling the leaf-margin [— 82.]
82a. Leaves with stipules[1a, in RUBIACEAE], p. 108.
82b. Leaves with a prominent ridge connecting them at the base [— 83.]
82c. Leaves with neither stipules nor connecting ridges[1a, in OLEACEAE], p. 88.
83a. Bundle-scar one in each leaf-scar[18b, in CAPRIFOLIACEAE], p. 110.
83b. Bundle-scars three in each leaf-scar (Honeysuckle)[12, in CAPRIFOLIACEAE], p. 110.
84a. Leaves compound [— 85.]
84b. Leaves simple [— 95.]
85a. Stems prickly or thorny [— 86.]
85b. Stems without prickles or thorns [— 88.]
86a. Leaves twice-pinnate[1a, in ARALIACEAE], p. 80.
86b. Leaves evenly pinnate[5b, in LEGUMINOSAE], p. 58.
86c. Leaves odd-pinnate or trifoliate [— 87.]
87a. Leaflets entire 1a,[1a, in RUTACEAE], p. 65.
87b. Leaflets serrate 3b,[3b, in ROSACEAE], p. 51.
88a. Leaflets 3 [— 89.]
88b. Leaflets 5 to many [— 91.]
89a. Tall shrubs; leaflets entire or minutely toothed[1b, in RUTACEAE], p. 65.
89b. Shrubs 2 m. high or less; leaves conspicuously toothed [— 90.]
90a. Stipules present[17b, in ROSACEAE], p. 53.
90b. Stipules none[1b, in ANACARDIACEAE], p. 68.
91a. Leaflets 6-25 mm. long [— 92.]
91b. Leaflets 30 mm. long, or more [— 93.]
92a. Leaflets mostly 5, rarely 3 or 7[7a, in ROSACEAE], p. 52.
92b. Leaflets mostly 9-19, 15 mm. long or more[26a, in LEGUMINOSAE], p. 60.
92c. Leaflets mostly 25-45, less than 15 mm. long[8a, in LEGUMINOSAE], p. 58.
93a. Leaflets entire[3a, in ANACARDIACEAE], p. 68.
93b. Leaflets entire, except for 1-4 large glandular teeth near their base[SIMARUBACEAE], p. 65.
93c. Leaflets toothed throughout [— 94.]
94a. Juice milky[1a, in ANACARDIACEAE], p. 68.
94b. Juice not milky[3a, in ROSACEAE], p. 51.
95a. Leaves minute, scale-like, appressed[2a, in CISTACEAE], p. 74.
95b. Leaves 3-10 mm. long, spreading, completely rolled into a tube[EMPETRACEAE], p. 68.
95c. Leaves normal in shape, green in color [— 96.]
96a. Leaves evergreen, as shown by their presence on the older parts of the stem[4b, in ERICACEAE], p. 84.
96b. Leaves deciduous [— 97.]
97a. Stems or branches thorny [— 98.]
97b. Stems or branches without thorns or thorny leaves [— 103.]
98a. Leaves conspicuously palmately veined [— 99.]
98b. Leaves pinnately veined, or sometimes with smaller lateral veins arising from the end of the petiole [— 100.]
99a. Leaves 5 cm. wide or less[1a, in SAXIFRAGACEAE], p. 49.
99b. Leaves 15 cm. wide or more[1a, in ARALIACEAE], p. 80.
100a. Leaves entire[5a, in SOLANACEAE], p. 100.
100b. Leaves toothed or somewhat lobed [— 101.]
101a. Leaves with bristly margins; some of the thorns three-pointed[2a, in BERBERIDACEAE], p. 40.
101b. Leaves not bristly on the margin; thorns not branched [— 102.]
102a. Only lateral thorns present[41b, in ROSACEAE], p. 54.
102b. Only terminal thorns present[2a, in RHAMNACEAE], p. 71.
103a. Leaves palmately veined, or with one or more pairs of lateral veins from the base of the leaf [— 104.]
103b. Leaves pinnately veined [— 111.]
104a. Leaves entire [— 105.]
104b. Leaves toothed [— 106.]
104c. Leaves palmately lobed [— 108.]
105a. Foliage fragrant when crushed; leaves ovate[1b, in LAURACEAE], p. 41.
105b. Foliage not aromatic; leaves heart-shape[3b, in LEGUMINOSAE], p. 58.
106a. Lateral veins straight and parallel, running to the teeth of the leaf[3a, in BETULACEAE], p. 22.
106b. Lateral veins curved or branched, and not running straight to the teeth [— 107.]
107a. Tall shrubs with somewhat milky juice and broadly ovate leaves[2b, in URTICACEAE], p. 23.
107b. Low shrubs less than 1 m. high with watery juice[1b, in RHAMNACEAE], p. 71.
108a. Leaves with 2 or 3 entire lobes, spicy-fragrant when crushed[1b, in LAURACEAE], p. 41.
108b. Leaves with milky juice[2b, in URTICACEAE], p. 23.
108c. Leaves neither spicy-fragrant nor with milky juice [— 109.]
109a. Stem covered with brown bristles[29, in ROSACEAE], p. 54.
109b. Stem not bristly [— 110.]
110a. Sides of the petiole strongly decurrent on the stem; bundle-scars crowded or nearly in contact in the leaf-scars[28b, in ROSACEAE], p. 53.
110b. Sides of petiole little decurrent or not at all; bundle-scars distinctly separate[2b, in SAXIFRAGACEAE], p. 49.
111a. Leaves aromatically fragrant when crushed [— 112.]
111b. Leaves not aromatically fragrant when crushed [— 113.]
112a. Leaves broadly obovate, entire; a common woodland shrub[1a, in LAURACEAE], p. 41.
112b. Leaves linear-lanceolate or oblanceolate, conspicuously toothed or entire[MYRICACEAE], p. 20.
113a. Leaves entire [— 114.]
113b. Leaves toothed or lobed [— 121.]
114a. Base of the petiole covering the axillary buds; twigs marked with rings[THYMELAEACEAE], p. 77.
114b. Base of petiole not covering the bud, and twigs not marked with rings [— 115.]
115a. Pith with prominent partitions; tall shrubs with fetid bark; leaves obovate, 10 cm. long or larger[ANONACEAE], p. 40.
115b. Pith not partitioned; leaves smaller [— 116.]
116a. Leaves waxy or resinous underneath[24b, in ERICACEAE], p. 86.
116b. Leaves not waxy or resinous [— 117.]
117a. Lateral veins curved forward and almost parallel to the margin of the leaf[2a, in CORNACEAE], p. 83.
117b. Lateral veins spreading [— 118.]
118a. Leaves lanceolate or linear, much longer than wide [— 119.]
118b. Leaves ovate or elliptical [— 120.]
119a. Stem weak, spreading or trailing[5a, in SOLANACEAE], p. 100.
119b. Stems, or some of them, erect[3b, in LEGUMINOSAE], p. 58.
120a. Leaves with purple petioles, which are at least one-fourth as long as the leaf-blade[1a, in AQUIFOLIACEAE], p. 69.
120b. Leaves with short petioles or sessile[24c, in ERICACEAE], p. 86.
121a. Lateral veins straight and parallel, mostly ending in the teeth of the leaf [— 122.]
121b. Lateral veins not straight and parallel [— 129.]
122a. Leaves 2-ranked, i. e., in two longitudinal rows, with the third leaf directly above the first [— 123.]
122b. Leaves not 2-ranked [— 127.]
123a. Leaves unsymmetrical, oblique at the base, i. e., with one side of the leaf larger than the other[HAMAMELIDACEAE], p. 51.
123b. Leaves symmetrical or nearly so at the base [— 124.]
124a. Lateral leaf-veins ending in the leaf-teeth [— 125.]
124b. Lateral veins not ending in the teeth[42b, in ROSACEAE], p. 55.
125a. Bark smooth and fluted on the large stems[1b, in BETULACEAE], p. 21.
125b. Bark rough or warty or glandular [— 126.]
126a. Leaves 4 cm. long or less[3a, in BETULACEAE], p. 22.
126b. Leaves 5 cm. long or more[9b, in BETULACEAE], p. 22.
127a. Pith 3-angled[6a, in BETULACEAE], p. 22.
127b. Pith 5-angled[13b, in FAGACEAE], p. 23.
127c. Pith cylindrical [— 128.]
128a. Leaves finely serrate[42b, in ROSACEAE], p. 55.
128b. Leaves coarsely or doubly serrate[41a, in ROSACEAE], p. 54.
129a. Leaves coarsely or doubly serrate [— 130.]
129b. Leaves simply serrate [— 131.]
130a. Leaves 2-ranked, i. e., in two longitudinal rows, with the third leaf directly over the first[9b, in BETULACEAE], p. 22.
130b. Leaves not 2-ranked[41a, in ROSACEAE], p. 54.
131a. Leaves with glands on the petiole or at the base of the leaf-blade [— 132.]
131b. Leaves with small dark glands on the upper side of the mid-vein[42a, in ROSACEAE], p. 54.
131c. Leaves without glands [— 133.]
132a. Willows; with usually slender leaves, frequently conspicuous broad stipules, and lateral buds protected by a single external bud-scale[13, in SALICACEAE], p. 20.
132b. Plums and cherries; with leaves lanceolate or broader, and stipules minute and falling early in the season; lateral buds with more than one bud-scale[30, in ROSACEAE], p. 54.
133a. With stipules or with stipular scars indicating where stipules have been detached [— 134.]
133b. Without stipules or stipular scars [— 138.]
134a. With three bundle-scars in each leaf-scar [— 135.]
134b. With one bundle-scar in each leaf-scar [— 136.]
135a. Willows; usually with slender leaves and twigs and frequently with large conspicuous stipules; lateral buds covered by a single external bud-scale[13, in SALICACEAE], p. 20.
135b. Juneberries; with oblong or ovate leaves and small stipules which fall early; lateral buds with more than one external scale[42b, in ROSACEAE], p. 55.
136a. Leaves mostly entire, only a few here and there with low teeth[1a, in AQUIFOLIACEAE], p. 69.
136b. Leaves sharply toothed [— 137.]
137a. Axillary buds superposed, i. e., with a second one just above the first[1b, in AQUIFOLIACEAE], p. 69.
137b. Axillary buds not superposed[2b, in RHAMNACEAE], p. 71.
138a. Leaves with purple petioles, which are at least one-fourth as long as the blade[1a, in AQUIFOLIACEAE], p. 69.
138b. Leaves short-petioled or sessile [— 139.]
139a. Stems erect and straight, unbranched or with very few branches[27, in ROSACEAE], p. 53.
139b. Stems more or less crooked and freely branched, making a spreading shrub[25, in ERICACEAE], p. 86.
— 140—
140a. Flowers appearing in autumn, after the leaves have fallen[HAMAMELIDACEAE], p. 51.
140b. Flowers appearing in spring, before the leaves have opened [— 141.]
141a. Flowers in catkins, without brightly colored or petal-like parts [— 142.]
141b. Flowers not in catkins, either with or without brightly colored or petal-like parts [— 149.]
142a. Leaves 2-ranked, as shown by the arrangement of buds and leaf-scars in two longitudinal rows, so that the third bud is directly over the first [— 143.]
142b. Leaves and leaf-scars not 2-ranked [— 146.]
143a. Bundle-scars three in each leaf-scar [— 144.]
143b. Bundle-scars several in each leaf-scar[2b, in URTICACEAE], p. 23.
144a. Leaf-buds with only 1-3 visible bud-scales[10, in BETULACEAE], p. 22.
144b. Leaf-buds with more than 3 visible scales [— 145.]
145a. Bark of the branches smooth and dark gray, the larger stems fluted with projecting longitudinal ridges[1b, in BETULACEAE], p. 21.
145b. Branches without projecting ridges[4, in BETULACEAE], p. 22.
146a. Pith 3-angled[8, in BETULACEAE], p. 22.
146b. Pith 5-angled[13b, in FAGACEAE], p. 23.
146c. Pith cylindrical [— 147.]
147a. Visible outer bud-scales 2 or more [— 148.]
147b. Buds with a single visible outer scale[13, in SALICACEAE], p. 20.
148a. Bundle-scars 3 in each leaf-scar[MYRICACEAE], p. 20.
148b. Bundle-scars more than 3 in each leaf-scar[2b, in URTICACEAE], p. 23.
149a. Flowers dark red-purple, about 3 cm. wide[ANONACEAE], p. 40.
149b. Flowers bright pink, irregular, about 1 cm. wide[3a, in LEGUMINOSAE], p. 58.
149c. Flowers white, with 5 conspicuous petals [— 150.]
149d. Flowers greenish or yellowish, small, inconspicuous [— 152.]
150a. Ovary 1, superior, i. e., in the center of the flower and not attached to surrounding parts[36, in ROSACEAE], p. 54.
150b. Ovary inferior, appearing as a swelling below the calyx at the apex of the pedicel [— 151.]
151a. Flowers in racemes or solitary[42b, in ROSACEAE], p. 55.
151b. Flowers in flattened or rounded branching clusters[42a, in ROSACEAE], p. 55.
152a. Stems thorny[1a, in RUTACEAE], p. 65.
152b. Stems not thorny [— 153.]
153a. Bark pleasantly aromatic when crushed; perianth with 6 parts [— 154.]
153b. Bark not pleasantly aromatic; perianth with 4 short lobes[THYMELAEACEAE], p. 77.
154a. Flowers in sessile lateral clusters[1a, in LAURACEAE], p. 41.
154b. Flowers in peduncled terminal clusters[1b, in LAURACEAE], p. 41.
— 155—
155a. Leaves narrow, needle-like or scale-like, mostly evergreen [— 54.]
155b. Leaves broader, flat or rolled, but not needle-like or scale-like — 156.
156a. Twining or climbing vines [— 56.]
156b. Not twining or climbing [— 157.]
157a. Leaves opposite [— 158.]
157b. Leaves alternate [— 165.]
158a. Leaves compound [— 68.]
158b. Leaves simple [— 159.]
159a. Leaves broad, palmately lobed [— 160.]
159b. Leaves not palmately lobed [— 161.]
160a. Flowers greenish-yellow, in racemes or panicles[2a, in ACERACEAE], p. 70.
160b. Flowers white, in rounded or flattened clusters[22a, in CAPRIFOLIACEAE], p. 111.
161a. Flowers in close clusters, subtended by four large white petal-like bracts[4b, in CORNACEAE], p. 83.
161b. Flowers small, white, in dense spherical heads[1a, in RUBIACEAE], p. 108.
161c. Flowers not in dense heads, and not subtended by petal-like bracts [— 162.]
162a. Petals separate from each other [— 163.]
162b. Petals united with each other [— 164.]
163a. Flowers dark purple-red[1b, in CELASTRACEAE]. p. 69.
163b. Flowers bright yellow[1a, in HYPERICACEAE], p. 73.
163c. Flowers pink-purple; aquatic shrubs[1a, in LYTHRACEAE], p. 77.
163d. Flowers white[5, in CORNACEAE], p. 83.
163e. Flowers minute, greenish; twigs usually thorny[1b, in RHAMNACEAE], p. 71.
163f. Flowers small, yellowish; leaves silvery beneath[ELAEAGNACEAE], p. 77.
164a. Stamens 2[1a, in OLEACEAE], p. 88.
164b. Stamens 4 or 5[11, in CAPRIFOLIACEAE], p. 110.
164c. Stamens 10[18a, in ERICACEAE], p. 85.
165a. Leaves once-compound [— 166.]
165b. Leaves simple [— 172.]
165c. Leaves twice- or thrice-compound[4a, in ARALIACEAE], p. 80.
166a. Flowers small, greenish or greenish-yellow [— 167.]
166b. Flowers conspicuous, white, or brightly colored [— 170.]
167a. Stems thorny[1a, in RUTACEAE], p. 65.
167b. Stems not thorny [— 168.]
168a. Leaflets 3, entire or minutely toothed[1b, in RUTACEAE], p. 65.
168b. Leaflets 3, conspicuously toothed[1b, in ANACARDIACEAE], p. 68.
168c. Leaflets more than 3 [— 169.]
169a. Leaflets entire except for 1-4 large glandular teeth near their base[SIMARUBACEAE], p. 65.
169b. Leaflets entire, or toothed for their entire length[ANACARDIACEAE], p. 68.
170a. Flowers with a single bright-blue petal[8a, in LEGUMINOSAE], p. 58.
170b. Flowers with several petals [— 171.]
171a. Flowers regular[3, in ROSACEAE], p. 51.
171b. Flowers irregular, the upper petal the largest[4, in LEGUMINOSAE], p. 58.
172a. Leaves minute, scale-like, appressed[2a, in CISTACEAE], p. 74.
172b. Leaves 3-10 mm. long, spreading, completely rolled into a tube[EMPETRACEAE], p. 68.
172c. Leaves normal in shape, green in color [— 173.]
173a. Leaves evergreen, as shown by their presence on the older parts of the stem[4b, in ERICACEAE], p. 84.
173b. Leaves deciduous [— 174.]
174a. Flowers in catkins, without petal-like parts [— 142.]
174b. Flowers not in catkins, either with or without petal-like parts [— 175.]
175a. Flowers small, inconspicuous, yellowish or greenish in color [— 176.]
175b. Flowers white or colored, with conspicuous petals [— 180.]
176a. Leaves broad and palmately lobed; stem thorny[1a, in ARALIACEAE], p. 80.
176b. Leaves entire, toothed, or with 2-3 entire lobes; stem not thorny [— 177.]
177a. Flowers in small axillary clusters; foliage not spicy-aromatic [— 178.]
177b. Flowers in clusters terminating last year's twigs; foliage spicy-aromatic[1b, in LAURACEAE], p. 41.
178a. Petals none; sepals present[2b, in RHAMNACEAE], p. 71.
178b. Petals present but small [— 179.]
179a. A stamen in front of each petal[2a, in RHAMNACEAE], p. 71.
179b. A stamen between each two petals[AQUIFOLIACEAE], p. 69.
180a. Petals united with each other; stamens 8-10[24, in ERICACEAE], p. 86.
180b. Petals separate from each other [— 181.]
181a. Petals 4 [— 182.]
181b. Petals 5 [— 183.]
181c. Petal-like sepals 6; real petals none; foliage spicy-aromatic[1b, in LAURACEAE], p. 41.
181d. Petals 6; sepals also present [— 187.]
182a. Flowers in late spring or early summer[2a, in CORNACEAE], p. 83.
182b. Flowers in autumn[HAMAMELIDACEAE], p. 51.
183a. Corolla irregular, the upper petal largest[3b, in LEGUMINOSAE], p. 58.
183b. Corolla regular, all petals alike in size and shape [— 184.]
184a. Stamens 5 [— 185.]
184b. Stamens 10 or more[24, in ROSACEAE], p. 53.
185a. Flowers in loose racemes or axillary clusters[2, in SAXIFRAGACEAE], p. 49.
185b. Flowers in branching clusters [— 186.]
186a. Leaves palmately lobed; stem thorny[1a, in ARALIACEAE], p. 80.
186b. Leaves not lobed; stem not thorny[1b, in RHAMNACEAE], p. 71.
187a. Flowers dark red-purple[ANONACEAE], p. 40.
187b. Flowers yellow[2a, in BERBERIDACEAE], p. 40.