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Rosaceae
See list of 33 genera in this familyDryas integrifolia Vahl. has been persistently reported to occur in New England since at least 1814. This early report by Pursh was based on a specimen collected by Peck in 1781 from the White Hills of Englée Island off the coast of Newfoundland. Fernald (1903) contended that an error occurred during preparation of the early flora where the White Hills of Newfoundland became confused with the White Mountains of New Hampshire. Therefore, D. integrifolia is not considered part of the New England tracheophyte flora.
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2a. Plants herbaceous, less than 1 m tall
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3a. Androecium with 4 stamens; petals absent; bractlets present and alternating with the sepals (i.e., an epicalyx is present); gynoecium with 1 (–3) ovaries, permanently enclosed within the hypanthium
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3b. Androecium with many stamens; petals present (absent in apetalous flowers of R. dalibarda); bractlets absent; gynoecium with 5–many ovaries, not enclosed within the hypanthium (in part)
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2b. Plants trees or shrubs (i.e., woody), commonly taller than 1 m
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4a. Gynoecium apocarpous, composed of 3–many distinct carpels; fruit an achene, follicle, capsule, or aggregate of drupes (a drupe in Rhodotypos)
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5a. Leaves opposite; fruit a drupe
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5b. Leaves alternate; fruit an achene, capsule, follicle, or aggregate of drupes
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6a. Petals yellow; fruit an achene (i.e., both dry and indehiscent)
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6b. Petals white to pink or red-purple; fruit an aggregate of drupes, follicle, or capsule (i.e., not both dry and indehiscent)
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7a. Fruit fleshy, indehiscent; petals 15–30 mm long; leaf blades 10–20 cm long (in part)
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7b. Fruit dry, dehiscent; petals 2–7 mm long; leaf blades 3–10 cm long
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8a. Leaf blades toothed or double-toothed (often 3-lobed in S. ×vanhouttei); stipules lacking; carpels not inflated in fruit, dehiscing on 1 suture
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8b. Leaf blades usually 3-lobed; stipules present (or at least stipule scars present on the branchlets); carpels prominently inflated in fruit, dehiscing on both sutures
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4b. Gynoecium syncarpous and composed of 2–5 carpels or consisting of a single carpel; fruit a pome, drupe, or 5-angled capsule
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9a. Leaf blades entire (sometimes serrate near the apex on vigorous shoots in Exochorda)
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10a. Flowers solitary at the apex of leafy branchlets, 4–5 cm in diameter; fruit a pome 30–50 mm in diameter; leaf blades 5–10 ×3–5 cm
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10b. Flowers borne 2–10 together in a raceme or corymb-like cyme, up to 3.5 cm in diameter; fruit a pome 5–7 mm in diameter or a capsule; leaf blades 0.7–6.5 ×0.5–3.5 cm
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11a. Inflorescence a raceme of 4–10 flowers; petals white, 12–20 mm long; fruit a 5-angled capsule with deep sinuses containing winged seeds
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11b. Inflorescence a corymb or corymb-like cyme with 2–4 flowers; petals pink, 3–4 mm long; fruit a red pome with (1–) 2 (–3) pyrenes
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9b. Leaf blades serrate to lobed (often subentire over part of the margin in Prunus pumila and some Amelanchier)
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12a. Flowers with 1 style; fruit a drupe; ovary superior
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12b. Flowers with 2–5 styles; fruit a pome; ovary inferior, or at least partly so in fruit (note: the ovary is superior in flower in the following genera)
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13a. Inflorescence a raceme (+/- a fascicle in A. bartramiana); ovary and fruit 10-locular
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13b. Inflorescence a cyme, umbel, or fascicle, in any case lacking an elongate, main axis; ovary and fruit 2- to 5-locular
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14b. Carpels papery or cartilaginous, easily opened to expose the seeds; styles connate at the base (distinct in Pyrus); plants unarmed or with thorns in Chaenomeles (often with thorn-like short shoots in Malus and Pyrus); leaf blades unlobed (usually lobed in Malus sieboldii)
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15a. Leaf midrib with a row of glands on the adaxial surface; petals 4–6 mm long; fruit 0.4–1 cm in diameter, astringent at maturity
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15b. Leaf midrib without a row of glands on the adaxial surface; petals 15–25 mm long (5–7 mm long in Sorbus alnifolia); fruit 0.6–12 cm in diameter, sweet or sour-sweet at maturity
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16a. Leaf blades prominently double toothed; petals 5–7 mm long (in part)
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16b. Leaf blades single toothed (sometimes lobed in some Malus); petals 15–25 mm long
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17a. Branchlets usually with thorns; carpels each with many ovules; stipules large and conspicuous, mostly 5–10 mm long
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17b. Branchlets without thorns (though the short-shoots often thorn-like); carpels each with 2 ovules; stipules small and/or caducous
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18a. Styles distinct; anthers ± red (i.e., anthocyanic); orifice of hypanthium nearly closed by a ring of tissue; pome pyriform or globose, with abundant sclerenchyma cells (i.e., with a gritty feel); inflorescence a corymb-like raceme; leaves involute in bud, with a thick, waxy cuticle on the adaxial surface
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18b. Styles connate at the base; anthers yellow to white (i.e., non-anthocyanic); orifice of hypanthium open; pome globose to ovoid, without or with few sclerenchyma cells (i.e., without a gritty feel); inflorescence a fascicle; leaves convolute or conduplicate in bud, without a thick, waxy cuticle adaxially
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20a. Gynoecium with 2–6 (–10) carpels
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21a. Petals white (sometimes pale pink); inflorescence at the apex of a leafy stem
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21b. Petals yellow; inflorescence on a ± naked peduncle originating from near the ground level, or sometimes with a small leaf or 2 immediately below the cyme
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22a. Leaflets toothed along the margins and at the apex; petals 5–10 mm long; androecium with many stamens (in part)
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22b. Leaflets 3 (–5) toothed at the very apex, the margins entire for much of their length; petals ca. 1 mm long; androecium with 5 stamens
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23a. Styles elongate, jointed near or above the middle, the basal portion with a hooked tip, becoming indurate and persistent in fruit, the apical portion deciduous [Fig. 844]; lower and upper stem leaves distinctly different in size, shape, and division (in part)
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23b. Styles short, not jointed near middle, deciduous in fruit [Fig. 839]; lower and upper stem leaves relatively similar in outline, though the upper somewhat reduced in size
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24a. Flowers without bractlets alternating with the sepals; carpels maturing as small drupes that are coherent in fruit; plants often armed with bristles or prickles (in part)
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24b. Flowers with bractlets that resemble the sepals and alternate with them (i.e., the sepals appear to number (8–) 10 per flower); carpels maturing as achenes; plants unarmed
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25a. Bractlets definitely larger than the sepals, with 3 conspicous teeth at the apex; receptacle enlarged in fruit but rather dry and insipid tasting; petals yellow (in part)
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25b. Bractlets of ± similar size as the sepals or smaller, lacking conspicuous apical teeth (though the margins may have small teeth); receptacle either enlarged in fruit and sweet-tasting or not enlarged and remaining dry; petals white to pink or ochroleucous to yellow
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26a. Receptacle enlarged in fruit and becoming fleshy, sweet-tasting at maturity; petals white or tinged with pink; bractlets ± subequal in size to the sepals
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26b. Receptacle neither enlarged nor fleshy in fruit; petals yellow or white; bractlets in most species narrower and/or shorter than the sepals
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27a. Style originating from the side of the carpel (i.e., lateral) [Fig. 839, L]; petals white; surface of ovary and achenes pubescent; leaflets entire for most of the margin and with 3 (–5) teeth at the very apex
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27b. Style originating from or very near the apex of the carpel (i.e., terminal) [Fig. 839, R]; petals yellow (white in P. alba); surface of ovary and achenes glabrous; leaflets with teeth or lobes usually distributed over more of the margin, restricted to the very apex in a few species (in part)
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19b. Leaves once- or twice-pinnately compound, always with more than 3 leaflets [Fig. 871]
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28a. Plants trees or shrubs (i.e., woody)
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29a. Flowers with 2–5 carpels; inflorescence a many-flowered cyme or panicle, usually with 25 or more flowers
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30a. Rachis of leaves adaxially with clusters of dark glands at the nodes; flowers with 2–4 carpels, partly epigynous; leaflet margins serrate to obscurely double-serrate [Fig. 871]; inflorescence a flat- to round-topped cyme; fruit a pome (in part)
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30b. Rachis of leaves lacking dark glands; flowers with 5 carpels, perigynous; leaflet margins double-serrate; inflorescence a tall panicle; fruit a follicle
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29b. Flowers with many carpels; inflorescence a solitary flower, a corymb, a cyme, or a raceme, most species with an inflorescence with fewer than 25 flowers
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31a. Plants unarmed; leaflets entire; fruit and hypanthium not fleshy; petals yellow (often white or ochroleucous in planted populations)
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31b. Plants usually armed with bristles or prickles; leaflets toothed; fruit fleshy or enclosed in a fleshy hypanthium; petals white to pink to red-purple or ochroleucous
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32a. Fruit an aggregate of achenes, surrounded and concealed by a fleshy hypanthium; stipules connate to the petiole for at least half their length [Fig. 862]; plants perennial
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32b. Fruit an aggregate of drupes, not surrounded by a hypanthium and, therefore, clearly visible [Fig. 869]; stipules distinct from the petiole; plants biennial—producing vegetative stems the first year and reproductive the second (in part)
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28b. Plants herbaceous (sometimes woody at the very base)
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33a. Leaves twice-pinnately compound; fruit dehiscent
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33b. Leaves once-pinnately compound; fruit indehiscent
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34a. Flowers with 4 petaloid sepals, 0 petals, and 0–2 carpels
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34b. Flowers with 5 sepaloid sepals, 5 petals, and 2–many carpels
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35b. Flowers with 5–many carpels; hypanthium not armed; inflorescence a solitary flower, a corymb, or a cyme
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36a. Styles elongate, jointed near or above the middle, the basal portion with a hooked tip, becoming indurate and persistent in fruit, the apical portion deciduous [Fig. 844]; lower and upper stem leaves distinctly different in size, shape, and division (in part)
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36b. Styles short, not jointed near the middle, deciduous in fruit; lower and upper stem leaves relatively similar in outline, though the upper somewhat reduced in size
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37a. Flowers without bractlets alternating with the sepals; petals white or pink to pink-red; carpels 5–15 per flower, arranged in a single whorl
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37b. Flowers with bractlets that resemble the sepals and alternate with them (i.e., the sepals appearing to number (8–) 10 per flower); petals yellow, white, or red; carpels many per flower, spirally arranged in several cycles
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38a. Flowers solitary at the tips of leafless peduncles produced from the nodes of an eventually prostrate to spreading stem
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39a. Leaves pinnately compound with 5–31 principal leaflets, conspicuously pubescent with gray-white tomentum on the abaxial surface (this sometimes partially concealed by lustrous, sericeous hairs); style lateral, emerging from the side of the carpel [Fig. 839, L]
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39b. Leaves palmately compound with 3–5 leaflets, glabrous or moderately pubescent with villous or sericeous hairs on the abaxial surface; style terminal, emerging from near the apex of the carpel [Fig. 839, R] (in part)
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38b. Flowers few to numerous, arranged in cymes borne at the summit of a leafy stem
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40a. Petals ochroleucous; style subbasal, emerging from near the base of the carpel; plants viscid-pubescent, especially above, the hairs with brown septa; stamens mostly 25–30 per flower
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40b. Petals red or yellow; style terminal or lateral; plants not viscid-pubescent; stamens mostly 20 per flower
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41a. Petals red; style originating from the side of the carpel (i.e., lateral) [Fig. 839, L]; principal leaves with 5–7 pinnately arranged leaflets; wetland species
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41b. Petals yellow; style originating from near the apex of the carpel (i.e., terminal) [Fig. 839, R]; leaves with 3–7 palmately or subpalmately arranged leaflets; primarily upland plants (in part)
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Each photo represents one genus in this family.