Acer

Keys in Flora of Pakistan

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Keys as per BSI Flora of India (Vol. 5) by M P Nayyar and Anukul Dutta

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1a Leaves unlobed (sometimes slightly 3-lobed in A. stachyophyllum and A. thomsonii) …..2.
b Leaves 3- to 7(–9)-lobed …..6.
2a Leaves unlobed or slightly 3-lobed, inflorescence racemose ……3.
b Leaves always unlobed, inflorescence paniculate or racemose ……4.
3a Leaf margin serrate, inflorescence glabrous, flowers 4-merous ….8. A. stachyophyllum
b Leaf margin sub-entire or repand, inflorescence villous, flowers 5-merous …..11. A. thomsonii
4a Leaves ovate, inflorescence racemose ……5. A. sikkimense
b Leaves oblong ovate, inflorescence broadly paniculate……..5.
5a Leaf margin sub-entire, often serrulate near apex, inflorescence glabrous ….. 3. A. laevigatum
b Leaf margin entire, inflorescence pubescent ……4. A. oblongum
6a Leaves 7-lobed, inflorescence paniculate or corymbose, glabrous …….7.
b Leaves 3–5-lobed, inflorescence racemose, paniculate, or corymbose, glabrous or pubescent ……8.
7a Leaf margin entire, inflorescence corymbose ……..1. A. cappadocicum
b Leaf margin serrate or serrulate, inflorescence paniculate ……2. A. campbellii
8a Inflorescence broadly paniculate ……..9.
b Inflorescence racemose ………10.
9a Leaves mostly 3-lobed, margin double serrate, serration acute, flowers 4-merous …..7. A. acuminatum
b Leaves 5-lobed, margin serrate, serration obtuse, flowers 5-merous …….9. A. caesium
10a Leaf margin entire or repand, inflorescence villous …..11. A. thomsonii
b Leaf margin serrate, inflorescence glabrous, pubescent, or villous ……11.
11a Inflorescence pubescent or villous  ……..12.
b Inflorescence glabrous …….13.
12a Leaf margin double serrate, inflorescence paniculate raceme, pubescent, samara glabrous, wings diverging at a 40– 55 deg. angle ……. 10. A. caudatum
b Leaf margin distantly serrate, inflorescence simple raceme, villous, samara villous, wings diverging at a 10–25 deg. angle …… 12. A. sterculiaceum
13a Leaf margin setosely serrate, flowers 5-merous, samara wings diverging at a 80–90o angle ….6. A. pectinatum
b Leaf margin serrate or double serrate, flowers 4-merous, samara wings diverging at a 20–55 deg. angle ….8. A. stachyophyllum

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5. Flowers in short, lax often +/- cymose racemes; leaves coarsely and unequally serrate, softly pubescent beneath or with conspicuous tufts of hair in vein axils beneath 5. A. stachyophyllum
+ Flowers in long slender spike-like racemes; leaves entire, senulate or more regularly serrate, glabrous beneath or with inconspicuous tufts of hair in vein axils … .. 6
6. Leaves sharply serrate; bud scales not persistent at flowering time 3. A. hookeri (syn. of Acer sikkimense subsp. sikkimense)
+ Leaves entire or obscurely semilate; bud scales often persistent at flowering time …… 4. A. sikkimense
7. Leaves not strongly reticulate, margins doubly serrate …….. 6. A. taronense syn. of Acer pectinatum subsp. taronense (Hand.-Mazz.) E. Murray
+ Leaves +/- strongly reticulate, margins entire to serrulate ……….. .. 8
8. Leaves elliptic to obovate, 8 — 15 x 4 — 13cm, with a tuft of long pale hairs at petiole insertion on upper surface when young, margins serrulate; mericarps diverging at right angles 7. A. osmastonii (syn. of Acer calcaratum Gagnep. as per POWO)
+ Leaves broadly ovate or suborbicular, 10 – 23 x 7 – 20cm, finely and shortly puberulous at base on upper surface when young, margins entire or obscurely serrate; mericarps ascending, sometimes almost parallel …. .. 8. A. thomsonii
9. Leaf margin quite entire .. .. 9. A. cappadocicum (Only Acer cappadocicum var. indicum (Pax) Rehder has distribution as per Catalogue of Life😉
+ Leaf margin serrate or serrulate, sometimes doubly so … .. 10
10. Leaf margin coarsely doubly serrate ….. .. 11. A. caudatum
+ Leaf margin finely serrulate or distantly but regularly serrate (rarely weakly doubly serrate in A. pectinatum) … .. 11
11. Mature leaves glabrous beneath, or with a few pale hairs in vein axils beneath, 5 – 7-lobed … .. 10. A. campbellii
+ Mature leaves usually pubescent beneath at least along veins, 3 – 5-lobed …. 12
I2. Branchlets slender; leaf margin closely serrate; pubescence reddish 12. A. pectinatum
+ Branchlets stout; leaf margin distantly serrate; pubescence whitish 13. A. sterculiaceum