6 
In preparing the original manuscript of this list, 
Miss Alice C. Atwood, reference librarian of the Bureau 
of llant Industry, United States Department of Agricul¬ 
ture, contributed botli ideas and facts and did much to 
make this list of value. 
The difficult work of typewriting on two different 
machines in a form suitable for photostat reproduction 
was carried out very efficiently by Miss Mary J. Francis. 
Her finished typewritten copy has been photographed and 
from the original negative a number of positive copies 
have been prepared. 
Walter T. Swingle 
April, 1923. 
