PRELIMINARY REVISION OF THE NORTH AMERICAN SPECTES 
OF CACTUS, ANHALONIUM, AND LOPHOPHORA, 
PREFATORY NOTE. 
In the fall of 1890 Dr. George Vasey, then Botanist of the Depart- 
ment of Agriculture, arranged with me to prepare a revision of North 
American Cactacee, Owing to the peculiar difficuity of preserving 
material the family was poorly represented, even in our leading her- 
baria. To secure a large amount of additional material in the way 
of specimens and field notes the Department authorized me to visit 
the region of the Mexican boundary during the summer of 1891. 
Preliminary to this exploration it was necessary to examine the Engel- 
mann collection of Caetacee, in the possession of the Missourl Botan- 
ical Garden. This collection, supplemented by the continual addi- 
tions made at the garden, is by far the largest collection of skeletons 
and living specimens in this country,and also contains the large 
majority of our types. 
In March, 1891, I visited this collection and made such notes as 
secmed necessary for use in the field, and in June, accompanied by Mr. 
W. HH. Evans and Mr. G, C. Nealley, | began field work in the neigh- 
borhood of El Paso, Tex. After ten days of exploration it was neces- 
sary for ine to leave the field work in charge of Mr. Evans, who, with 
Mr. Nealley, continued work westward. during July and a part of 
August, to southern California, along the Southern Pacific Railway. 
As a result a large number of complete plant bodies was secured, but 
very few of them were in flower and the field notes indicated little 
besides collecting stations. During the following fall and winter pre- 
liminary determinations of this material were made by Mr. Evans. 
In the fall of 1892 critical study of this and other collections was 
begun in connection with my assistants, Dr. Eimon M. Fisher and Mr. 
Edwin B. Uline, who have ever since rendered constant and most impor. 
tant assistance in the examination of material and bibliography, which 
alone has made the work possible in the midst of other pressing duties. 
In the spring of 1895 these two gentlemen spent several weeks at 
the Missouri Botanical Garden in the critical study of its rich material, 
and during the latter part of their stay I assisted in the work. Dr. 
William Trelease, the director of the garden, had hastened the arrange- 
ment of the Engelmann material, and had mounted in convenient form 
the large mass of notes left by Dr. Engelmann. These notes contained 
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