170 
IOWA ACADEMY OE 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. 
* Staminate floive'. s , 3 — 6 together ; fruit destitute of an involucre , winged. 
Betula. Stamens, 2; filaments, 2-cleft; each division with an anther cell. 
Alnus. Stamens, 4; filaments, simple; anther cells, adnate. 
** Staminate flowers solitary; fruit involucrate, wingless 
Corylus. Nut enclosed by a leafy involucre. 
Ostrya. Nut at the base of an oblong enclosed bag. 
Carpinus.. Nut subtended by a large foliaceous bract. 
Betula nigra L. Sp. PI. 982, 175B. 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 lanulosa Mx. 
FI. Bor. Am. 2, 18L 
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, Yol. 1, p. 188; Arthur, Contr. to 
the Flora of Iowa, p. 29; Sargent, Forest Trees of North 
America, p. 161; Pammel, Proc. Iowa Acad, of Sciences, 
Yol. 1, pt. 2, 1890-91, p. 91; Iowa Geol. Sur., Yol. 10, p. 812; 
