10a. Leaves deeply pinnately lobed --11.

10b. Leaves crenate, dentate, or sinuate, not lobed --12.

11a. Leaf divided nearly to the middle by a pair of deep lateral lobes near the middle of the leaf; acorn more than half covered by the cup =Bur Oak, Quercus macrocarpa.=

11b. Leaf without a median pair of deeper lobes; acorn about one-fourth covered by the cup =White Oak, Quercus alba.=

12a. Leaves broadest at or near the middle, with numerous (8-13) sharp coa.r.s.e teeth on each side =Yellow Oak, Quercus muhlenbergii.=

12b. Leaves broadest above the middle, with a few shallow, rounded or subacute teeth (7 or less on each side) --13.

13a. Large tree; leaves densely white-tomentose beneath; acorn on a stalk 3-10 cm. long =Swamp White Oak, Quercus bicolor.=

13b. Shrub; leaves thinly white-tomentose beneath; acorn sessile or nearly so =Scrub Oak, Quercus prinoides.=

URTICACEAE, the Nettle Family

Herbs or trees, with small inconspicuous apetalous flowers.

1a. Trees or tall shrubs --2.

1b. Herbs --7.

2a. Leaves oblong-ovate to lanceolate, serrate --3.

2b. Leaves broadly ovate to rotund, some of them lobed (Mulberry) --6.

3a. Leaves thick, coa.r.s.ely and doubly serrate, broadest near the middle (Elm) --4.

3b. Leaves thin, simply serrate, broadest distinctly below the middle =Hackberry, Celtis occidentalis.=

4a. Some of the branches with flat corky wings; leaves smooth above =Cork Elm, Ulmus racemosa.=

4b. Branches without corky wings; leaves more or less rough above --5.

5a. Petioles and axillary buds glabrous =White Elm, Ulmus americana.=

5b. Petioles and axillary buds p.u.b.escent with rusty hairs =Slippery Elm, Ulmus fulva.=

6a. Leaves rough above =Red Mulberry, Morus rubra.=

6b. Leaves smooth above =White Mulberry, Morus alba.=

7a. Leaves alternate --8.

7b. Leaves opposite --9.

8a. Leaves 2-5 cm. long, stems p.u.b.escent =Pellitory, Parietaria pennsylvanica.=

8b. Leaves 8-20 cm. long; stem armed with stinging hairs =Wood Nettle, Laportea canadensis.=

9a. Twining plant; leaves serrate or cleft =Hop, Humulus lupulus.=

9b. Erect plant; leaves palmately compound =Hemp, Cannabis sativa.=

9c. Erect plants; leaves not lobed or compound --10.

10a. Stems armed with stinging hairs --11.

10b. Stems glabrous or rough, but not with stinging hairs --12.

11a. Leaves ovate, with a heart-shape base =Stinging Nettle, Urtica dioica.=

11b. Leaves lanceolate or ovate-lanceolate, not heart-shape at base =Slender Nettle, Urtica gracilis.=

12a. Stems glabrous, pellucid =Clearweed, Pilea pumila.=

12b. Stems rough, opaque =False Nettle, Boehmeria cylindrica.=

SANTALACEAE, the Sandalwood Family

Low herbs with alternate entire leaves and terminal cl.u.s.ters of small greenish-white bell-shape flowers without petals in spring and early summer.

1a. Inflorescence of several-flowered cl.u.s.ters terminating the stem and in the upper axils =Toad-flax, Comandra umbellata.=

1b. Inflorescence of axillary cl.u.s.ters of 1-5 flowers =Toad-flax, Comandra livida.=

LORANTHACEAE, the Mistletoe Family

Parasitic plants, attached to the branches of trees.

One species in Michigan, a dwarf brown plant 5-20 mm. long, with minute scale-like leaves, growing on the branches of Black Spruce =Dwarf Mistletoe, Arceuthobium pusillum.=

ARISTOLOCHIACEAE, the Birthwort Family