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Carya

See list of 5 species in this genus

Manning (1950) gave one of the most thorough accounts of the morphological details of Carya that are important for identification, including their variation through the growing season. Anyone serious about learning the genus Carya should spend time studying this work. Details of the terminal buds are important for identification. Caution is needed because some branchlets are terminated by pseudoterminal buds, especially those bearing fruit. Pseudoterminal buds, which can identified by the presence of a twig scar proximal to the bud, differ both in size and in the shape of outer scales compared with terminal buds. Similarly, details of leaf pubescence are especially important for identification. Though technically there exists more than one type of hair in Carya that appears to be compound (specifically, it appears to be a stellate hair with multiple rays emerging from the same point), they are not distinguished here due to practical difficulties in separating them. Therefore, hairs of the leaf blades surfaces are described here only as simple or compound. References: Manning (1950), Stone (1997).

  • 1a. Terminal bud yellow or orange-yellow to yellow-brown, with 4–6 valvate scales; leaves with (5–) 7–9 (–13) leaflets; exocarp (i.e., husk) 2–3 mm thick, the sutures narrowly winged; staminate aments borne, in part, on reduced, ± leafless shoots that originate on the branches of the previous season
  • 1b. Terminal bud light brown to red-brown or dark brown, with 6–15 imbricate scales; leaves with 3–9 (–11) leaflets; exocarp 3–15 mm thick (as thin as 2 mm in C. glabra), the sutures usually unwinged; staminate aments borne only at base of leafy shoots on branchlets of the current season
    • 2a. Leaflets strongly ciliate with tufts of hairs borne below the apex of the marginal 
teeth [Fig. 688]; leaves with (3–) 5 (–7) leaflets; pedicels and bracts of the staminate 
flowers glabrous
    • 2b. Leaflets at maturity becoming eciliate or retaining some cilia, but without subapical tufts of hairs on the marginal teeth; leaves with (3–) 5–9 (–11) leaflets; pedicels and/or bracts of staminate flowers pubescent
      • 3a. Leaflets abaxially glabrous to pubescent with mostly simple hairs, some compound hairs with 2–4 rays also present; terminal bud 5–15 mm long, the bud scales abaxially glabrous to hirsute; branchlets relatively slender, (1.8–) 2–4.1 (–4.4) mm thick, glabrous or nearly so; exocarp 2–5 mm thick
      • 3b. Leaflets abaxially pubescent with simple hairs and abundant compound hairs with 2–8 (–17) rays; terminal bud 8–20 mm long, the bud scales abaxially tomentose; branchlets stout, (3.5–) 4–9 mm thick, hirsute (sometimes becoming subglabrous in 
 C. laciniosa); exocarp 4–13 mm thick
        • 4a. Petiole and rachis densely hirsute; leaflets usually acute at the apex, pubescent predominately with compound hairs, the simple hairs scarce; branchlets red-brown; bark ridged, not exfoliating; exocarps rough but glabrous
        • 4b. Petiole and rachis sparely pubescent to subglabrous; leaflets usually acuminate at apex, pubescent with both simple and compound hairs; branchlets light orange-brown to light yellow-brown; bark separating into long strips or broad plates; exocarps minutely hirsute

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