A MONOGRAPH OF THE NORTH AMERICAN 
USNEACE. 
BY R. HEBER HOWE, JR. 
Parr I, 
It is my purpose to issue in parts a monograph of the North 
American Usneacex. The work will embody the results of 
my studies of the family which have extended over a period 
of nearly ten years. These studies have been made afield in 
all the distributional zones of our area, and with the aid of 
many important herbaria in both this country and Europe. 
It is hoped this work will supply a manual for future research 
in this most difficult! and interesting family of plants. 
CLASSIFICATION. 
In my paper on the Classification de la Famille des 
Usneacex dans l’Amerique du Nord (Theses présentées a la 
Faculté des Sciences de ]’Université de Paris pour obtenir 
le titre de Docteur de l'Université, Série 60, ordre 71, 1-32: 
1912; and Mycologia, 4: 152-153. 1912) will be found a 
complete study of the taxonomy of this family, which I have 
followed here with only a few minor changes. Below is 
given the working hypothesis on which this classification is 
based. 
Division: 
THALLOPHYTES. 
Origin. 
(Symbiotic) 
Subdivision: (a) Composition of the thallus, 
Class: (a) Method of spore production. 
1 Harmand, Lich., France, 372. 1907. 
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