BI 463 Plant Taxonomy
Spring 2000

Acer negundo, Acer sp., Aesculus, Ailanthus, Albizia, Alnus, Amelanchier, Aralia,
Asimina, Betula, Carpinus, Carya cordiformis, Carya sp, Catalpa, Celtis,
Cephalanthus, Cercis, Chionanthus, Cornus, Diospyros, Euonymous, Fagus, Fraxinus,
Juglans, Lindera, Liquidambar, Liriodendron, Maclura, Magnolia, Morus, Nyssa,
Ostrya, Oxydendrum, Paulownia, Platanus, Populus, Prunus, Quercus, Rhamnus,
Rhus, Robinia, Salix, Sassafras, Staphylea, Tilia, Ulmus

All images were taken at 7x and are proportional

1. Leaf scars opposite or whorled . . . . . . . . . . . . . . . . . . . . . .2
1. Leaf scars alternate . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2. Twig stout; leaf scars large . . . . . . . . . . . . . . . . . . . . . . .3
2. Twig slender; leaf scars small . . . . . . . . . . . . . . . . . . . . . .6

3. Terminal bud absent . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminal bud present . . . . . . . . . . . . . . . . . . . . . . . . . . .5

4. Leaf scars mostly whorled; lateral buds solitary. . . . . .  . . . .Catalpa
4. Leaf scars mostly opposite; lateral buds often superposed. . . . . . . . . .
   . . . . . . . . . . . . . . . . . . . . . . . . . . . .  Paulownia tomentosa

5. Terminal bud with 4-6 scales; leaf scars crescent-shaped or half-round
   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fraxinus
5. Terminal bud with ca. 12 scales; leaf scars sheild-shaped or triangular . .
   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aesculus

6. Terminal bud absent; stipular scars prominent . . . . . . . . . . . . . . 7
6. Terminal bud present; stipular scars absent or indistinct. . . . . . . . .8

7. Stipules persistent or their scars connecting leaf scars; leaf scars nearly
   circular, the 1 bundle scar crescent or U-shaped. Cephalanthus occidentalis
7. Stipules deciduous, scars not connecting leaf scars; leaf scars half-round,
   bundle scars 3 or more . . . . . . . . . . . . . . . . .Staphylea trifolia

8. Twigs 4-angled, green . . . . . . . . . . . . . . . . . . . . . . Euonymous
8. Twigs not 4-angled, may be green or not . . . . . . . . . . . . . . . . . 9

9. Leaf scar with 1 bundle scar and it U-shaped; twigs with warty lenticels;
   lateral buds sometimes superposed . . . . . . . . . . . . . . . Chionanthus
9. Leaf scar with 3 bundle scars; twigs with lenticels prominent or not but
   never particularly warty; lateral buds usually single . . . . . . . . . 10

10. Terminal bud with 2 valvate scales; lateral buds very small covered by
    persistent petiole bases in last season’s leaf scars . . . .Cornus florida
10. Terminal bud with more than 2 scales; lateral buds moderate, not hidden. 11

11. Twigs typically bright green; buds wooly; opposite leaf scars nearly
    touching . . . . . . . . . . . . . . . . . . . . . . . . . . .Acer negundo
11. Twigs reddish or brownish; buds not wooly; opposite leaf scars not
    touching but connected by a ridge . . . . . . . . . . . . . . . . Acer sp.

12. Twigs armed with thorns, spines, or prickles . . . . . . . . . . . . . . 13
12. Twigs not armed . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

13. Spines paired at the nodes; terminal but absent; lateral buds hidden; leaf
    scar split from beneath by developing bud . . . . . . Robinia pseudoacacia
13. Spines single at nodes or scattered over surface of stem . . . . . . . . 14

14. Spines or prickles scattered over surface of stem; terminal bud present;
    leaf scar nearly encircling the thick stem with single row of bundle scars
     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aralia spinosa
14. Single spine above leaf scar; terminal bud absent; leaf scars rounded;
    twigs moderate, not thick . . . . . . . . . . . . . . . . Maclura pomifera

15. Terminal bud present . . . . . . . . . . . . . . . . . . . . . . . . . . 16
15. Terminal bud absent . . . . . . . . . . . . . . . . . . . . . . . . . . .30

16. Buds naked, without scales . . . . . . . . . . . . . . . . . . . . . . . 17
16. Buds with 1 or more scales . . . . . . . . . . . . . . . . . . . . . . . 18

17. Bundle scars 3; stipular scars present; the naked buds wooly . . . . . .
    . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rhamnus caroliniana
17. Bundle scars 5-7; stipular scars absent; the naked bud rusty pubescent;
    leaf scars partially surrounding bud . . . . . . . . . . . Asimina triloba

18. Bundle scar 1, transverse, linear, sometimes divided into 3 parts; twigs green;
    bud scales with central rib; stipular scars absent . . . . . Sassafras albidum
18. Bundle scars 3 to many; twigs not green; stipular scars present or absent. .19

19. Bud scales 2, valvate and somewhat like a duck’s bill; stipular scars encircling
    twig . . . . . . . . . . . . . . . . . . . . . . . Liriodendron tulipifera
19. Bud scales 1, 3 or more; stipular scars present or absent . . . . . . . 20

20. Bud scale 1; stipular scars encircling twig, bundle scars numerous,
    scattered. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Magnolia
20. Bud scales 3 or more; stipular scars present or absent; bundle scars
    3 or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

21. Bundle scars many, scattered or in 3 groups; stipular scars absent . . . 22
21. Bundle scars 3; stipular scars present or absent . . . . . . . . . . . . 25

22. Buds sulfurous yellow; 2-4 valvate scales . . . . . . . . Carya cordiformis
22. Buds not yellow; scales imbricate . . . . . . . . . . . . . . . . . . . .23

23. Buds clustered at end of twig; leaf scars raised, half-round; bundle
    scars scattered . . . . . . . . . . . . . . . . . . . . . . . . . . Quercus
23. Buds usually not clustered at twig end; leaf scars shield-shaped or 3-lobed;
    bundle scars usually in 3 groups . . . . . . . . . . . . . . . . . . . . 24

24. Bundle scars in 3 U-shaped groups; terminal bud scales covered with dense
    pubescence . . . . . . . . . . . . . . . . . . . . . . . . . Juglans nigra
24. Bundle scars in 3 circular groups or scattered; bud scales less hairy;
    outer bud scales often broken off, exposing inner scales . . . . . . Carya

25. Terminal bud often sticky resinous; lowermost scale of lateral bud ~large
    and directly above leaf scar; stipular scars present . . Populus deltoides
25. Not as above; stipular scars present or absent . . . . . . . . . . . . . 26

26. Bundle scars as white rings with dark centers; twigs often with corky wings
    . . . . . . . . . . . . . . . . . . . . . . . . . .Liquidambar styraciflua
26. Not as above . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

27. Terminal bud elongated, several times longer than broad . . . . . . . . .28
27. Terminal bud only slightly longer than broad . . . . . . . . . . . . . . 29

28. Buds distinctly cigar-shaped with 10-24 scales; faint stipular scars nearly
    encircle twig . . . . . . . . . . . . . . . . . . . . . .Fagus grandifolia
28. Buds with fewer scales and slightly curved; stipular scars absent . . . . .
    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Amelanchier

29. Small, often indistinct stipular scars present; lenticles on lower twig
    becoming horizontally elongated . . . . . . . . . . . . . . Prunus serotina
29. Stipular scars absent; lenticels small, not prominent . . . Nyssa sylvatica

30. Leaf scar rounded, surrounded by an elevated rim and thus appearing concave;
    numerous raised bundle scars; stipular scars present . . . . . . . .   Morus
30. Leaf scar not surrounded by an elevated rim; stipular scars present or absent
    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

31. Bundle scar 1, elongated and curved; stipular scars absent . . . . . . . 32
31. Bundle scars 3 or more; stipular scars present or absent . . . . . . . . 33

32. Twig green to red, glabrous; buds partially embedded in bark and with
    3-6 scales . . . . . . . . . . . . . . . . . . . . . . . . Oxydendrum arboreum
32. Twig gray to red-brown, glabrous or pubescent; buds not embedded and with
    2 overlapping scales . . . . . . . . . . . . . . . . . Diospyros virginiana

33. Bud with single cap-like scale . . . . . . . . . . . . . . . . . . . . . 34
33. Bud with more than 1 scale or buds naded . . . . . . . . . . . . . . . . 35

34. Twigs moderate; stipular scar forming a ring around twig; leaf scar narrow,
    nearly encircling axillary bud; bundle scars 5-9. . Plantanus occidentalis
34. Twigs slender; stiplular scars present or absent; bundle scars 3. . . Salix

35. Stipular scars absent . . . . . . . . . . . . . . . . . . . . . . . . . 36
35. Stipular scars present (may be indistinct). . . . . . . . . . . . . . . 40

36. Bundle scars many; twig moderate to very stout . . . . . . . . . . . . . 37
36. Bundle scars (2)3; twig slender . . . . . . . . . . . . . . . . . . . . .39

37. Twig very stout; leaf scar large and heart-shaped; bundle scars in a row
    near edge of leaf scar . . . . . . . . . . . . . . . . Ailanthus altissima
37. Twigs stout to moderate; leaf scars not heart-shaped; bundle scars
    scattered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

38. Leaf scar horseshoe-shaped, nearly encircling bud; twigs glabrous . . . .
    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Rhus glabra
38. Leaf scar broadly crescent-shaped; twigs pubescent . . . . . Rhus copallina

39. Twigs reddish brown; leaf scar fringed at top . . . . . . Cercis canadensis
39. Twigs greenish; leaf scar not fringed at top . . . . . . . .Lindera benzoin

40. Leaf scar 3-lobed or tending to be so, with dark shiny margin; twig with
    large conspicuous lenticels . . . . . . . . . . . . . Albizia julibrissin
40. Leaf scar not 3-lobed, lenticels prominent or not . . . . . . . . . . . 41

41. Bud scales 3(4) or fewer; buds never less than 1 mm long . . . . . . . . 42
41. Bud scales 4 or more (buds may be 1 mm or less in length in some taxa) . 44

42. Buds asymmetrical (lopsided); stipular scars prominent . . . . . . . Tilia
42. Not as above . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

43. Buds distinctly stalked, with 2-3 valvate scales . . . . . Alnus serrulata
43. First pair of bud scales forming a V-shaped angle above the leaf scar;
    bud scales with hairy margins . . . . . . . . . . . . . . . . Betula nigra

44. Bundle scars slightly depressed; bud often positioned slightly to one side
    of leaf scar . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ulmus
44. Not as above . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

45. Buds very small (often less than 1 mm long) and closely appressed to stem .
     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Celtis
45. Buds larger (usually more than 1 mm long) . . . . . . . . . . . . . . . .46

46. Buds uniform in size; bud scales numbering about 6 and with fine
    longitudinal striations  . . . . . . . . . . . . . . . . . Ostrya virginiana
46. Buds of 2 distinct sizes; bud scales numbering 6-12 and without striations
     . . . . . . . . . . . . . . . . . . . . . . . . . . . Carpinus caroliniana