SUMMER KEY TO THE GENERA [A]

a.Leaves simple.
b.Leaves needle-shaped, awl-shaped, strap-shaped or scale-like.
c.Leaves in clusters of 2-many.
d.Leaves in clusters of 2-5, sheathed, persistent forseveral years.PINUS, p. [4].
dd.Leaves in fascicles of 8-many, on short, lateral branchlets,deciduous in autumn.LARIX, p. [17].
cc.Leaves solitary, not clustered.
d.Leaves opposite.
e.Twigs flattened; leaves all of one kind, scale-like,decurrent on the stem; fruit a small, pale browncone.THUJA, p. [31].
ee.Twigs essentially terete; leaves of two kinds, eitherscale-like, or else awl-shaped, often both kinds onthe same branch, not decurrent on the stem; fruitberry-like, bluish.JUNIPERUS, p. [33].
dd.Leaves alternate or spirally-whorled.
e.Leaves flattened, soft to the touch.
f.Leaves 1/2-1-1/4 inches long, sessile, aromatic; cones2-4 inches long; bark of trunk with raised blisterscontaining resin.ABIES, p. [27].
ff.Leaves seldom over 1/2 inch long, short-petioled,not aromatic; cones about 3/4 inch long; bark oftrunk without raised blisters.TSUGA, p. [29].
ee.Leaves 4-sided, harsh to the touch.PICEA, p. [18].
bb.Leaves broad and flat.
c.Leaves alternate or clustered, never opposite nor whorled.
d.Margin of leaves entire or only slightly undulate.
e.Leaves heart-shaped or rounded; fruit a legume.CERCIS, p. [167].
ee.Leaves oval, ovate or obovate; fruit not a legume.
f.Branches armed with stout, straight spines; fruitlarge, orange-like.MACLURA, p. [133].
ff.Branches without spines; fruit small, not orange-like.
g.Fruit an acorn.QUERCUS, p. [96].
gg.Fruit a drupe or berry.
h.Twigs spicy-aromatic when bruised; leaves ofmany shapes on the same branch.SASSAFRAS, p. [139].
hh.Twigs not spicy-aromatic; leaves not of manyshapes on the same branch.
i.Leaves thick, abruptly pointed, very lustrousabove, not clustered at the ends of thebranches.NYSSA, p. [209].
ii.Leaves thin, long-pointed, not lustrousabove, clustered at the ends of the branches.CORNUS, p. [202].
dd.Margin of leaves serrate, toothed or lobed.
e.Margin of leaves serrate to toothed.
f.Branches armed with stiff, sharp thorns.CRATAEGUS, p. [151].
ff.Branches not armed.
g.Base of leaves decidedly oblique.
h.Leaf-blades about as long as they are broad,heart-shaped.TILIA, p. [201].
hh.Leaf-blades 1-1/2 - 2 times as long as they arebroad, oval to ovate.
i.Leaves thin, coarsely but singly serrate;fruit a globular drupe, ripe in autumn.CELTIS, p. [131].
ii;Leaves thick, coarsely and doubly serrate;fruit a samara, ripe in spring.ULMUS, p. [122].
gg.Base of leaves essentially symmetrical.
h.Teeth coarse, 2-5 per inch of margin.
i.Leaves very glabrous both sides; fruit aprickly bur.
j.Leaves 3-5 inches long, very lustrousbeneath; bark close, smooth, steel-gray.FAGUS, p. [93].
jj.Leaves 6-8 inches long, not lustrous beneath;bark fissured, brownish.CASTANEA, p. [95].
ii.Leaves pubescent or white-tomentose, atleast beneath; fruit not a prickly bur.
j.Leaves 2-4 inches long, broadly ovate tosuborbicular; fruit a very small capsule,falling in spring.POPULUS, p. [44].
jj.Leaves 4-7 inches long, oblong-lanceolateto obovate; fruit an acorn, falling inautumn.QUERCUS, p. [96].
hh.Teeth fine, 6-many per inch of margin.
i.Leaf-petioles laterally compressed; leavestremulous.POPULUS, p. [44].
ii.Leaf-petioles terete; leaves not tremulous.
j.Leaf-blades at least 3 times as long asthey are broad.
k.Twigs brittle; fruit a very small capsule,falling in spring.SALIX, p. [34].
kk.Twigs tough; fruit a fleshy drupe, fallingin late summer or autumn.PRUNUS, p. [152].
jj.Leaf-blades not more than twice as longas they are broad.
k.Leaf-blades about twice as long as theyare broad.
l.Margin of leaves singly serrate; fruitfleshy.
m.Lenticels conspicuous; pith whitishor brownish; bark easily peeledoff in papery layers; buds ovoid.PRUNUS, p. [152].
mm.Lenticels inconspicuous; pithgreenish; bark not separable intopapery layers; buds narrow-conical.AMELANCHIER, p. [149].
ll.Margin of leaves doubly serrate; fruitnot fleshy.
m.Trunk fluted; fruit inclosed withina halberd-shaped involucre.CARPINUS, p. [83].
mm.Trunk not fluted; fruit not inclosedwithin a halberd-shapedinvolucre.
n.Bark of trunk gray-brown, broken into narrow,flattish pieces loose at the ends; fruit in hop-like strobiles.OSTRYA, p. [81].
nn.Bark of trunk white, yellow ordark brown, platy or cleaving offin papery layers; fruit not inhop-like strobiles.BETULA, p. [84].
kk.Leaf-blades almost as broad as theyare long.
l.Lower side of leaves more or lessdowny; sap milky; leaves not crowdedon short, spur-like branchlets; fruitberry-like, black.MORUS, p. [135].
ll.Lower side of leaves glabrous; sapnot milky; leaves crowded on short,spur-like branchlets; fruit a large,green pome.PYRUS, p. [142].
ee.Margin of leaves distinctly lobed.
f.Fruit an acorn.QUERCUS, p.96.
ff.Fruit not an acorn.
g.Leaves fan-shaped, with many fine veins radiatingfrom the base of the blade.GINKGO, p. [3].
gg.Leaves not fan-shaped, without many fine veinsradiating from the base of the blade.
h.Leaf-lobes entire.
i.Leaf-petioles 5-6 inches long; leaves lustrousabove; twigs not aromatic when bruised.LIRIODENDRON, p. [137].
ii.Leaf-petioles about 1 inch long; leaves dullabove; twigs spicy-aromatic when bruised.SASSAFRAS, p. [139].
hh.Leaf-lobes sinuate-toothed to serrate.
i.Leaf-lobes coarsely sinuate-toothed.PLATANUS, p. [141].
ii.Leaf-lobes serrate.
j.Branches armed with stiff, sharp thorns;sap not milky.CRATAEGUS, p. [151].
jj.Branches unarmed; sap milky.MORUS, p. [135].
cc.Leaves opposite or whorled.
d.Margin of leaves entire or only slightly undulate.
e.Leaves 3-5 inches long; spray fine; fruit an ovoid,scarlet drupe.CORNUS, p. [202].
ee.Leaves 5-12 inches long; spray coarse; fruit a long,slender-cylindrical capsule.CATALPA, p. [222].
dd.Margin of leaves serrate to lobed.
e.Margin of leaves finely serrate.VIBURNUM, p. [229].
ee.Margin of leaves distinctly lobed.ACER, p. [172].
aa.Leaves compound.
b.Leaves alternate.
c.Leaves simple-pinnate.
d.Branchlets armed with short, sharp prickles.ROBINIA, p. [169].
dd.Branchlets unarmed.
e.Leaflets entire with the exception of 2 or morecoarse, glandular teeth at the base.AILANTHUS, p. [171].
ee.Leaflets serrate the entire length.
f.Upper leaflets less than 1 inch broad.
g.Trunk and large branches armed with stoutspines; leaflets 3/4-1-1/2 inches long.GLEDITSIA, p. [165].
gg.Trunk and large branches unarmed; leaflets 2-3inches long.PYRUS, p. [142].
ff.Upper leaflets 1-5 inches broad.
g.Leaflets 5-11; pith homogeneous.CARYA, p. [66].
gg.Leaflets 11-23; pith chambered.JUGLANS, p. [60].
cc.Leaves bi-pinnate.
d.Trunk and large branches armed with stout spines;leaflets 3/4 - 1-1/2 inches long.GLEDITSIA, p. [165].
dd.Trunk and large branches unarmed; leaflets 2 - 2-1/2inches long.GYMNOCLADUS, p. [163].
bb.Leaves opposite.
c.Leaves pinnately compound; fruit a samara.
d.Leaflets 3-5; samaras paired.ACER, p. [172].
dd.Leaflets 7-11, exceptionally 5; samaras not paired.FRAXINUS, p. [210].
cc.Leaves digitately compound; fruit a prickly bur.AESCULUS, p. [194].

WINTER KEY TO THE GENERA[B]

a.Leaves persistent and green throughout the winter, needle-shaped,awl-shaped or scale-like.
b.Leaves in clusters of 2-5, sheathed.PINUS, p. [5].
bb.Leaves solitary, not clustered.
c.Leaves opposite.
d.Twigs flattened; leaves all of one kind, scale-like,decurrent on the stem; fruit a small, pale brown cone.THUJA, p. [31].
dd.Twigs essentially terete; leaves of two kinds, eitherscale-like, or else awl-shaped, often both kinds on thesame branch, not decurrent on the stem; fruit berry-like,bluish.JUNIPERUS, p. [33].
cc.Leaves alternate or spirally-whorled.
d.Leaves flattened, soft to the touch.
e.Leaves 1/2 - 1-1/4 inches long, sessile, aromatic; cones2-4 inches long; bark of trunk with raised blisterscontaining resin.ABIES, p. [27].
ee.Leaves seldom over 1/2 inch long, short-petioled, notaromatic; cones about 3/4 inch long; bark of trunkwithout raised blisters.TSUGA, p. [29].
dd.Leaves 4-sided, harsh to the touch.PICEA, p. [19].
aa.Leaves not persistent and green throughout the winter, butdeciduous in early autumn.
b.Twigs, branches or trunks armed with stiff, sharp prickles,spines or thorns.
c.Thorns or spines not exceeding 1/2 inch in length on thebranches.
d.Spines in pairs at each node; buds rusty-hairy, 3-4superposed; fruit a flat pod.ROBINIA, p. [169].
dd.Spines one at each node; buds glabrous, not superposed;fruit orange-like. MACLURA, p. [133].
cc.Thorns or spines much exceeding 1/2 inch in length onthe branches.
d.Thorns usually branched, situated above the nodes;lateral buds superposed, the lower covered by bark;fruit a flat pod.GLEDITSIA, p. [165].
dd.Thorns unbranched on twigs, situated at the nodes;lateral buds not superposed, not covered by bark;fruit a small pome.CRATAEGUS, p. [151].
bb.Twigs, branches or trunks unarmed.
c.Leaf-scars mainly crowded on short, stout, lateral shoots.
d.Bundle-scar 1; fruit a cone, usually present.LARIX, p. [17].
dd.Bundle-scars 2; fruit a globose drupe falling inautumn.GINKGO, p. [3].
cc.Leaf-scars distributed along the lateral branches.
d.Leaf-scars (or some of them) 3 at a node, i. e.,whorled.CATALPA, p. [223].
dd.Leaf-scars 1-2 at a node, i.e., not whorled.
e.Leaf-scars 2 at a node, i.e., opposite.
f.Terminal buds 1/2 - 1-1/2 inches long, resin-coated;twigs very stout.AESCULUS, p. [195].
ff.Terminal buds rarely exceeding 1/2 inch in length,not resin-coated; twigs not conspicuously stout.
g.Leaf buds with 1 pair of scales visible.
h.Buds scurfy-pubescent.VIBURNUM, p. [229].
hh.Buds glabrous.CORNUS, p. [203].
gg.Leaf buds with 2 or more pairs of scales visible.
h.Bundle-scars usually 3, distinct, separated.ACER, p. [174].
hh.Bundle-scars many, minute, more or less confluentin a U-shaped line.FRAXINUS, p. [211].
ee.Leaf-scars 1 at a node, i.e., alternate.
f.Bundle-scars 1-3.
g.Bundle-scar only 1, or appearing as 1.
h.Twigs bright green, spicy-aromatic; bundle-scarappearing as a horizontal line; terminalbud present; pith homogeneous.SASSAFRAS, p. [139].
hh.Twigs brownish, not spicy-aromatic; bundle-scarappearing as a large dot; terminal budabsent; pith chambered.CELTIS, p. [131].
gg.Bundle-scars 3 or in 3 compound, but distinctgroups.
h.Terminal bud present.
i.Stipule-scars present.
j.First scale of lateral bud directly in front,i.e., exactly above the center of the leaf-scar;twigs brittle; pith somewhat star-shapedin cross-section.POPULUS, p. [45].
jj.First scale of lateral bud not directly infront, i. e., to one side of the center of theleaf-scar; twigs not brittle; pith circularin cross-section.PRUNUS, p. [153].
ii.Stipule-scars absent.
j.Buds bright to dark red, the terminal1/8 - 1/4 inch long.
k.Branches contorted, bearing manyshort, spur-like branchlets; fruit anapple an inch or more in diameter, lightgreen.PYRUS, p. [143].
kk.Branches not contorted, not bearingshort, spur-like branchlets; fruit berry-like,1/2 inch long, blue-black.NYSSA, p. [209].
jj.Buds brownish to gray, the terminal exceeding1/4 inch in length.
k.Buds narrow-conical, sharp-pointed;leaf-scars small, narrowly crescent-shaped;twigs about 1/16 inch thick;pith homogeneous; fruit berry-like, notpresent.AMELANCHIER, p. [149].
kk.Buds broadly conical to ovoid, blunt-pointed;leaf-scars conspicuous, broadlyheart-shaped; twigs about 1/4 inchthick; pith chambered; fruit a nut,often present.JUGLANS, p. [61].
hh.Terminal bud absent (sometimes present onshort shoots of Betula).
i.Stipule-scars present.
j.Bud-scale only 1 visible; twigs brittle.SALIX, p. [34].
jj.Bud-scales 2 or more; twigs not brittle.
k.Bark smooth, close, warty or peelinginto papery layers, but not flaky norrough-ridged.
l.Tip of bud appressed; fruit berry-like.CELTIS, p. [131].
ll.Tip of bud not appressed; fruit notberry-like.
m.Trunk fluted; catkins not presentin winter; lenticels not elongatedhorizontally; low tree or bushyshrub.CARPINUS, p. [83].
mm.Trunk not fluted; catkins usuallypresent in winter; lenticels elongatedhorizontally; large trees.BETULA, p. [85].
kk.Bark flaky or rough-ridged, not wartynor peeling off in papery layers.
l.Bundle-scars depressed, conspicuous;bark thick, more or less deeply furrowed.ULMUS, p. [123].
ll.Bundle-scars not depressed, inconspicuous;bark thin, broken into narrow,flattish strips, loose at the ends.OSTRYA, p. [81].
ii.Stipule-scars absent.
j.Buds silky-pubescent, depressed; twigsstout, clumsy, blunt, with conspicuousleaf-scars.GYMNOCLADUS, p. [163].
jj.Buds glabrous, not depressed; twigs slender,with inconspicuous leaf-scars.
k.Buds 1/8 inch long, obtuse, somewhatflattened and appressed; pith with reddishlongitudinal streaks.CERCIS, p. [167].
kk.Buds 1/8-1/4 inch long, acute, not flattenednor appressed; pith without reddishstreaks.PRUNUS, p. [153].
ff.Bundle-scars 4-many.
g.Bundle-scars in a single U-shaped line.
h.Terminal bud present; fruit berry-like; ashrub or small tree.PYRUS, p. [143].
hh.Terminal bud absent; fruit not berry-like;large trees.
i.Stipule-scars present; twigs slender.
j.Stipule-scars encircling the twig; leaf-scarsnearly surrounding the bud; barkpeeling off in thin plates, exposing thelighter colored inner bark.PLATANUS, p. [141].
jj.Stipule-scars not encircling the twig; leaf-scarsnot nearly surrounding the bud;bark thick, rough-ridged, not exposing theinner bark.ULMUS, p. [123].
ii.Stipule-scars absent; twigs very stout.
j.Bundle-scars usually not more than 5.GYMNOCLADUS, p. [163].
jj.Bundle-scars usually 6-12.AILANTHUS, p. [171].
gg.Bundle-scars variously grouped or scattered,but not in a single line.
h.Terminal bud present.
i.Stipule-scars present.
j.Stipule-scars encircling the twig; visiblebud-scales 2, united.LIRIODENDRON, p. [137].
jj.Stipule-scars not encircling the twig; visiblebud-scales more than 2, not united.
k.Buds 4 times as long as broad, notclustered at the tips of vigorous shoots;fruit a prickly bur.FAGUS, p. [93].
kk.Buds not 4 times as long as broad,usually clustered at the tips of vigorousshoots; fruit an acorn.QUERCUS, p. [98].
ii.Stipule-scars absent.CARYA, p. [67].
h.Terminal bud absent (occasionally present inCastanea).
i.Bud at end of twig very obliquely unsymmetrical,mucilaginous when chewed.TILIA, p. [201].
ii.Bud at end of twig symmetrical, not mucilaginouswhen chewed.
j.Bud-scales 2-3 visible; pith star-shaped incross-section; sap not milky; fruit aprickly bur, present; large tree.CASTANEA, p. [95].
jj.Bud-scales 4-8 visible; pith not star-shapedin cross-section; sap milky; fruitberry-like, not present; small tree.MORUS, p. [135].

MANUAL OF TREES