Jones: Flora of Illinois, 102. Rhamnaceae 179 



3. Leaves 3-5-lobed, the lobes unequally crenate-serrate; petals 5; ovary 

 glabrous; samaras incurved, glabrous at maturity. 

 4. Leaves glabrous or nearly so on the lower surface at maturity; ma- 

 ture twigs glabrous; samaras 18-25 mm. long, the wing 6-8 mm. 



wide; woods, local. Mar. -Apr. Red Maple A. rubrum L. 



4. Leaves permanently tomentose beneath; twigs more or less pubescent 

 at maturity; samaras 3.5-6 cm. long, the wing 1-2 cm. broad at the 

 middle; swamps, rare, s. Ill A. drummondii H. & A. 



2. Leaves not silvery-white beneath; flowers corymbose, unfolding with the 

 leaves. 



5. Leaves flat, 3-5-lobed, the lobes coarsely dentate, more or less glabrous; 

 stipules absent; woods, common. Apr. -May. [/I. barbatum Michx.; 

 A. saccharophorum K. Koch.; Saccharodendron barbatum NieuwI.} 

 Sugar Maple A. saccharum Marsh. 



5. Leaves with drooping sides, usually with 3 main lob^s, the lobes acumi- 

 nate, entire or undulate or obtusely toothed; lower surface yellowish 

 green and softly pubescent, at least along the veins, varying to nearly 

 glabrous in age; stipules often present, large, enclosing the buci; 

 woods, local. May. Black Maple A. nigrum Michx. f. 



1. Leaves 3-7-foliolate; flowers dioecious, drooping, appearing before the leaves; 

 anthers linear, apiculate; disk none; petals none; alluvial soil, common. 



Apr. -May. [Negundo nuttallii (NieuwI.) Rydb.] Box-elder 



A. negundo L. 



101. HiPPOCASTANACEAE T. Sc G. — Horse-chestnut Family 

 1. Aesculus L. — Horse-chestnut 



1. Ovary and capsule soft-spiny; flowers 12-18 mm. long, finely pubescent, 

 greenish yellow; stamens exserted; calyx campanulate, 6-8 mm. long; 

 woods, common. Apr.-May. Ohio Buckeye A. glabra Willd. 



1 . Ovary and capsule smooth; flowers about 3 cm. long, reddish purple or yel- 

 lowish; stamens included; woods, s. 111. Apr.-May. Yellow or Sweet 

 Buckeye A. octandra Marsh. 



102. Rhamnaceae Dum. — Buckthorn Family 



1. Leaves pinnately veined; flowers greenish yellow; fruit a drupe 1. Rhamnus 



1 . Leaves triple-veined ; flowers (in our species) white, fragrant; fruit a capsule 



2. Ceanolhus 



1. Rhamnus L. — Buckthorn 

 1 . Winter buds scaly. 



2. Leaves opposite or subopposite, ovate, abruptly acute; twigs rigid, often 

 spine-like; flowers usually 4-merous; petals present; drupe with 3 or 4 

 nutlets; roadsides and edges of woods, occasional in n. III.; nat. from 

 Eurasia. May-June R. cathartica L. 



2. Leaves alternate; native shrubs 1-2 m. tall; twigs not at all spine-like. 



