Michigan Trees Part 4

cc. Leaves alternate or spirally-whorled.

d. Leaves flattened, soft to the touch.

e. Leaves 1/2 - 1-1/4 inches long, sessile, aromatic; cones 2-4 inches long; bark of trunk with raised blisters containing resin. ABIES, p. 27.

ee. Leaves seldom over 1/2 inch long, short-petioled, not aromatic; cones about 3/4 inch long; bark of trunk without 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, but deciduous in early autumn.

b. Twigs, branches or trunks armed with stiff, sharp p.r.i.c.kles, spines or thorns.

c. Thorns or spines not exceeding 1/2 inch in length on the branches.

d. Spines in pairs at each node; buds rusty-hairy, 3-4 superposed; 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 on the 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 in autumn.

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-p.u.b.escent. 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 confluent in 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-scar appearing as a horizontal line; terminal bud present; pith h.o.m.ogeneous.

Sa.s.sAFRAS, p. 139.

hh. Twigs brownish, not spicy-aromatic; bundle-scar appearing as a large dot; terminal bud absent; pith chambered. CELTIS, p. 131.

gg. Bundle-scars 3 or in 3 compound, but distinct groups.

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-shaped in cross-section. POPULUS, p. 45.

jj. First scale of lateral bud not directly in front, i. e., to one side of the center of the leaf-scar; twigs not brittle; pith circular in cross-section. PRUNUS, p. 153.

ii. Stipule-scars absent.

j. Buds bright to dark red, the terminal 1/8 - 1/4 inch long.

k. Branches contorted, bearing many short, spur-like branchlets; fruit an apple an inch or more in diameter, light green. PYRUS, p. 143.

kk. Branches not contorted, not bearing short, spur-like branchlets; fruit berry-like, 1/2 inch long, blue-black.

NYSSA, p. 209.

jj. Buds brownish to gray, the terminal exceeding 1/4 inch in length.

k. Buds narrow-conical, sharp-pointed; leaf-scars small, narrowly crescent-shaped; twigs about 1/16 inch thick; pith h.o.m.ogeneous; fruit berry-like, not present. AMELANCHIER, p.

149.

kk. Buds broadly conical to ovoid, blunt-pointed; leaf-scars conspicuous, broadly heart-shaped; twigs about 1/4 inch thick; pith chambered; fruit a nut, often present. JUGLANS, p. 61.

hh. Terminal bud absent (sometimes present on short shoots of _Betula_).