28 American Midland Naturalist Monograph No. 2 



3. Leaves usually serrate or smuale-dentate as well as lobed. 

 4. Trees. 



5. Leaf -lobes not serrate or sinuate; blades white-tomentose beneath at first; 



flowers and fruits in catkins Populus in 38. Salicaceae 



5. Leaf-lobes serrate or sinuate-toothed. 



6. Flowers and fruits in dense, globose heads. 



7. Leaf-lobes serrate; leaves glabrous or pubescent, never white-tomentose; 



2-year old branchlets often corky-ridged 



Liquidambar in 81. Hamamelidaceae 



7. Leaf-lobes sinuate-toothed; blades white-tomentose beneath when young, 

 becoming nearly glabrous at maturity; branchlets terete; bark ex- 

 foliating 82. Platanaceae 



6. Flowers in catkins; pistillate flowers ripening into a succulent multiple fruit 



(a mulberry) ; leaf-lobes serrate-dentate Morus in 44. MoRACEAE 



4. Shrubs. 



8. Stamens 5; ovary inferior; fruit a berry; branches sometimes spiny or 



prickly 80. Grossulariaceae 



8. Stamens numerous; carpels 2-5, superior, separate, or united at the base, 



becoming follicles; branches never spiny; bark becoming shreddy 



- ....Phvsocarpus in 83. RoSACEAE 



1 . Leaves pinnately veined. 

 9. Lobes of the leaves serrate or crenate. 



10. Fruit of 2-5 follicles; bark shreddy; flowers in corymbs; branches never spiny 



Phvsocarpus in 83. RosACEAE 



10. Fruit a pome; branches often spiny. 



II. Flowers in cymes; styles united below the middle; pome large, the carpels 

 papery or leathery; branches (but not the twigs) sometimes with rather 



blunt spines Mains in 83. RosACEAE 



11. Flowers in corymbs; styles free; pomes small, the carpels bony; branches 



(and twigs) often with sharp spines Crataegus in 83. RosACEAE 



9. Lobes of the leaves not serrate. 



12. Leaves with a truncate apex and two broad lateral lobes; buds covered by the 



membranous stipules; flowers large Liriodendron in 60. MagNOLIACEAE 



12. Leaves not truncate at apex; flowers small. 



13. Leaves pmnatiftd with many rounded lobes on each side of the midvein; 

 monoecious shrub with fragrant foliage; flowers in erect catkins; fruit an 



ovoid nutlet surrounded by subulate bracts 39. Myricaceae 



13. Leaves with few lobes. 



14. Leaves with three principal veins from the base, aromatic; flowers yellow, 

 6-8 mm. broad, in racemes 3-5 cm. \ong-. -Sassafras in 68. Lauraceae 

 14. Leaves with I principal vein from the base, not aromatic; flowers green- 

 ish, the staminate in catkins; fruit an acorn. ...Qiicrciis in 42. Fagaceae 



Section 16. Trees and Shrubs With Alternate, Simple Leaves, 

 the Blades Toothed but Not Lobed 



], Base of blade symmetrical or nearly so. 



2. Flowers, at least the staminate (except Fagus) in catkins. 



3. Fruit a small several-seeded capsule, the seeds with a tuft of silky hairs; both 

 staminate and pistillate flowers m catkins; stigmas 2, often 2-lobed (sometimes 



3) ; dioecious shrubs or trees 38. Salicaceae 



3. Fruit not a capsule; seeds without a tuft of silky hairs; styles 2 or 3. 

 4. Fruit a 1-loculed, 1 -seeded nut; i)lants monoecious. 



5. Styles 3 42. Fagaceae 



5. Style 2-cleft, or stigmas 2 41. BeTULACEAE 



4. Fruit a juicy multiple fruit; plants often with milky juice; styles 2 



44. Moraceae 



2. Flowers never in catkins. 



6. Leaves with 1 principal vein from the base. 



