80 
SILVA OF NORTH AMERICA. 
BETULACEZ. 
of between four and six thousand feet above the sea-level, along the banks of streams with Willows, 
Sycamores, and Walnuts. 
It is common in the mountain canons of northern Mexico, and ranges 
through southern Mexico and Central America to the Andes of Peru, where the species was discovered 
by Humboldt.’ 
The wood of Alnus acuminata has not been examined. 
1 Several of the so-called varieties of this species from Mexico 
and Central America, if judged only by the fragments preserved 
in herbaria, might be considered species. The following, however, 
appear to be identical with the tree of New Mexico and Arizona: 
Bourgeau, No. 244, City of Mexico. — Lumholtz, No. 323, Sierra 
Madre. — Pringle, No. 5057, State of Michoacan, near Patzcuaro. — 
Pringle, No. 4361, Valley of Mexico. — Nelson, No. 1956, Huaju- 
pan. Better knowledge than is now obtainable with regard to the 
Mexican and Central American Alders may show that the species 
of northern Mexico is distinct from the Andean Alnus acuminata, 
in which case the name for this tree would appear to be Alnus 
oblongifolia of Torrey. 
EXPLANATION 
Puate CCCCLVII. 
. A flowering branch, natural size. 
. Seale of a staminate ament, rear view, with flowers, enlarged. 
NO oP WO DH 
OF THE PLATE. 
ALNUS ACUMINATA. 
A staminate flower, enlarged. 
. Pistillate flowers with their scale, front view, enlarged. 
. A fruiting branch, natural size. 
. Scale of a strobile, front view, with nuts, enlarged. 
. A nut cut transversely, enlarged. 
