Acer 



ACERACEAE 



655 



Leaves 5-lobed. 



Petioles glabrous or with some pubescence at the base and point of insertion. 



4. A. nigrum. 



Petioles pubescent their entire length 4a. A. nigrum f. pubescens. 



Leaves 3-lobed. 



Petioles glabrous 4b. A. nigrum var. Palmeri. 



Petioles pubescent 4c. A. nigrum var. Palmeri f. villosum. 



Leaves not yellow green beneath, the sides not drooping; petioles of the terminal 



pair of leaves not expanded at the base. 

 Leaves 5-lobed. 



Petioles glabrous 5. A. saccharum. 



Petioles pubescent their entire length 5a. .4. saccharum f. Schneckii. 



Leaves 3-lobed 5b. A. saccharum var. Rugelii. 



1. Acer Neg-undo L. (Nieuwland. Box-elders, real and so-called. 

 Amer. Midland Nat. 2: 129-142. 1911.) Boxelder. Map 1362. Usually 

 infrequent. In low ground along streams and rarely far from them on 

 higher ground in woods and along fences and roadsides. In some of the 

 low woods along streams in the southwestern part of the state this species 

 is common, and a nuisance as a forest tree because of its inferior quality. 



N. E. to Minn., southw. to Fla. and e. Tex. 



la. Acer Negundo var. violaceum Kirchner. (Farwell. Botanical glean- 

 ings in Michigan. III. Amer. Midland Nat. 10: 37. 1926.) Map 1363. 

 Found in the habitat of the species. 



Mass., Ohio, n. Wis., Minn., S. Dak. to Idaho, southw. to Mo. 



2. Acer saccharinum L. Silver Maple. Map 1364. Infrequent to fre- 

 quent and locally abundant in most parts of the state. It is always found 

 in wet places, usually in soil with little organic matter except in the lake 

 region ; along streams and about lakes and sloughs and low places in woods. 



N. B. to S. Dak., southw. to Fla. and Tex. 



3. Acer rubrum L. Red Maple. Map 1365. This and the preceding 

 species are known in commerce as soft maples in contrast to the hard or 

 sugar maples. Infrequent, except locally, in all parts of the state. In 



