Michigan Trees Part 3

f. Fruit an acorn. QUERCUS, p.96.

ff. Fruit not an acorn.

g. Leaves fan-shaped, with many fine veins radiating from the base of the blade. GINKGO, p. 3.

gg. Leaves not fan-shaped, without many fine veins radiating from the base of the blade.

h. Leaf-lobes entire.

i. Leaf-petioles 5-6 inches long; leaves l.u.s.trous above; twigs not aromatic when bruised. LIRIODENDRON, p. 137.

ii. Leaf-petioles about 1 inch long; leaves dull above; twigs spicy-aromatic when bruised. Sa.s.sAFRAS, p. 139.

hh. Leaf-lobes sinuate-toothed to serrate.

i. Leaf-lobes coa.r.s.ely sinuate-toothed. PLATa.n.u.s, 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 coa.r.s.e; 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 p.r.i.c.kles. ROBINIA, p.

169.

dd. Branchlets unarmed.

e. Leaflets entire with the exception of 2 or more coa.r.s.e, 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 stout spines; leaflets 3/4-1-1/2 inches long. GLEDITSIA, p. 165.

gg. Trunk and large branches unarmed; leaflets 2-3 inches long. PYRUS, p. 142.

ff. Upper leaflets 1-5 inches broad.

g. Leaflets 5-11; pith h.o.m.ogeneous. 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 - 2-1/2 inches 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 p.r.i.c.kly 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 cl.u.s.ters of 2-5, sheathed. PINUS, p. 5.

bb. Leaves solitary, not cl.u.s.tered.

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, either scale-like, or else awl-shaped, often both kinds on the same branch, not decurrent on the stem; fruit berry-like, bluish.

JUNIPERUS, p. 33.