THE GENUS CEREUS AND ITS ALLIES IN NORTH AMERICA, 
By N. L. Brirron and J. N. Roser. 
INTRODUCTION. 
Studies of North American Cactaceae, conducted now for several 
years in the museums and greenhouses at New York and Washington 
and supplemented by field work in the West Indies, Mexico, and the 
southwestern United States, have rendered us familiar with the habit 
and morphology of a large number of species. The information thus 
obtained makes it clear that a considerable number of generic types 
must be recognized, additional to those established by previous 
authors, in order to present a rational classification of this family. 
We have been greatly aided in our study by A. Berger’s admirable 
paper entitled, “‘A systematic revision of ‘the genus Cereus Mill.”* 
This is by far the most satisfactory treatment of the group which has 
everappeared. We think, however, that he has erred in referring to 
Cereus the genera Cephalocereus and Echinocereus, which are now 
almost universally considered distinct. 
But it is also true that these units have no more claim to generic rank 
than most of the other subgenera established by him. While, there- 
fore, we differ from Mr. Berger as to the importance of these groups, 
we realize that he has been consistent and logical in his work. The 
genera have very distinct flower and fruit characters as well as clearly 
defined habit and stem structure. We have experienced some difli- 
culty in forming a lineal arrangement of the genera which seemed to 
be logical. Mr. Berger’s arrangement as given in his synopsis of the 
subgenera of Cereus is in the main satisfactory but has certain defects. 
We have formed a new arrangement which will be followed here, 
although further study will doubtless lead to various changes in it. 
Although the present paper deals only with North American species, 
we may express the conviction incidentally that Eulychnia of Philippi 
and Cleistocactus of Lemaire, South American groups, should be re- 
stored to generic rank. 
In the present communication we submit a list, with bibliographic 
references and indication of geographic distribution and of type local- 
ities, of the genera and species with descriptions of the genera. 
Plates LXV and LXVI and LXVIII to LX XIII are from photo- 
graphs furnished by Dr. D. T. MacDougal, which are here used by 
courteous permission of the Carnegie Institute of W ashington. 
a Rep. Mo. Bot. ‘Gard. 16: 57-86. 1905. 
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