170 IOWA ACADEMY OF SCIENCES. 



decided preference for the eastern half of the state. The 

 alder and the cherry birch are local or quite limited in 

 their distribution, the former occurring in northeastern 

 Iowa, while the latter may be found in central Iowa. The 

 paper birch occurs in northeastern Iowa, a region noted 

 for many species found nowhere else in our state. 



* Stdniinatefloweis. 3 — 6 together; fruit destitute of an invnlucre, winged. 

 Betula. Stamens, 2; filaments, 2-cleft; each division with an anther cell. 

 Alnus. Stamens, 4; filaments, simple; anther cells, adnate. • 

 ** Stmninate flowers solitary; fruit involucrate, ivingless 

 CoRYLUS. Nut enclosed by a leafy involucre. 

 OsTRY..\. Nut at the base of an oblong enclosed bag. 

 Carpinus. Nut subtended by a large foliaceous bract. 



Betula nigra L. Sp. PI. 982, 1753. Red or River Birch. A 

 tree, usually thirty to sixty feet high and one to two feet 

 in diameter, with reddish or greenish brown bark, and red- 

 dish twigs; peduncles, shoots, and petioles soft downy; 

 leaves rhombic-ovate, acute at both ends, irregularly 

 doubly-serrate, downy beneath when young; nutlet one- 

 seeded, one-celled, broadly winged. Betula laiinlosa Mx. 

 Fl. Bor. Am. 2, ISL 



The species is frequent in the eastern half of the state, 

 less frequent elsewhere. The wood is hard, brown, strong, 

 and of rather light weight. The bark from the branches 

 separates into membranous layers. The species occurs in 

 alluvial soil along rivers. The wood is used for fuel and to 

 some extent for lumber which is used in furniture. The 

 pioneers made ox-yokes from this birch. 



Our specimens are from Johnson and Decatur counties. 

 We have observed the species in Allamakee, . Clayton, 

 Dubuque, Jackson, Clinton, Wapello, Linn, Appanoose, 

 Jefferson, and Ringgold counties. The State university 

 herbarium has specimens from Delaware, Scott, Muscatine 

 Louisa, Des Moines, and Polk counties. Professor Fink 

 reports the species from Fayette county; Professor Pam- 

 mel from Hardin county; and Mr. Mills by letter from 

 Henry county. 



White, Geol. Sur. Iowa, Vol. 1, p. 138; Arthur, Contr. to 

 the Flora of Iowa, p. 29; Sargent, Forest Trees of North 

 America, p. 161; Pammel, Proc. Iowa Acad, of Sciences, 

 Vol. 1, pt. 2, 1890-91, p. 91; Iowa Geol. Sur., Vol. 10, p. 312; 



