108 American Midland Naturalist Monograph No. 7 



sandy banks and dunes in the western and northwestern 



counties. May. [Schmaltzia arenaria Greene] 



R. arenaria (Greene) G.N.Jones 



50. Aceraceae J.St.Hil. — Maple Family 



1. Acer L. — Maple 



1 . Leaves simple, palmately-lobed ; floral disk present ; anthers ellip- 

 soid, not apiculate. 

 2. Leaves silvei-y-whitish or glaucous on the lower surface; flowers 

 in dense sessile clusters, appearing before the leaves. 

 3. Leaves 5-Iobed, the lobes serrate or cleft or parted; petals 

 none; ovary tomentose; samaras divergent, pubescent; 

 chiefly in alluvial soil, common. Mar. -Apr. Silver Maple 



- A. saccharinurn L. 



3. Leaves 3- to 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; mature twigs glabrous; samaras 18-25 mm 



long, the wing 6-8 mm wide; woods, local; chiefly in 



southern 111., but also in Cook, Lake, and McHenry 



counties. Mar.-Apr. Red Maple ...A. rubruni 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, southern 111. 



A. drumrnondii H.&A. 



2. Leaves not silvery-white beneath ; flowers corymbose, appearing 

 with the leaves. 

 6. Leaves flat, 3- to 5-lobed, the lobes coarsely dentate, more or 

 less glabrous; stipules absent; woods, common. Apr.-May. 



Sugar Maple A. saccharum Marsh. 



6. Leaves with drooping sides, usually with 3 main lobes, the 

 lobes acuminate, 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 bud; woods, local; May. 



Black Maple A. nigrum Michx.f. 



1. Leaves 3- to 7-foliolate; trees dioecious; flowers greenish, droop- 

 ing on slender pedicels, slightly before the leaves; anthers linear, 

 apiculate; disk none; petals none; alluvial soil, common. Apr.- 

 May. Box-elder A. negundo L. 



51. Rhamnaceae R.Br. — Buckthorn Family 



1. Leaves pinnately-veined; flowers greenish-yellowish; fruit a drupe 



1. Rhamnus 



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



capsule 2. Ceanothus 



