SYNOPSIS OF THE CACTACEZ OF THE UNITED STATES. 151 
For those who naturally may be horrified at the idea of 117 species of Cactacee in a territory 
where a few years ago scarcely half a dozen were known, I will indicate how the mass of material 
may be comprehended under fewer types. 
Of Mamillarie the species 1-9 are quite distinct, and can in no manner be united; 10-12 
might perhaps be considered as forms of a single species; 13-17 are all very distinct; 18 and 19, 
20-23, 25 and 26, 27 and 28 may possibly be forms of only 4 types, instead of 10, as I have 
enumerated them, — thus referring my 30 species to 22 types. 
n the genus Echinocactus the following species might be united: 1 and 2, 7 and 8, 9 and 10, 
12 and 13, 14 and 15,— leaving 15 instead of 20 types. 
The following species of Cereus will perhaps bear reduction: Nos. 1 and 2, 3 and 4, 5-7, 
10 and 11, 12-14, 16 and 17, 18-22 (though some of them, of which I do not even know the 
flowers, may prove to belong even to different sections !), 23 and 24, — thus reducing my 31 species 
to 18 types. 
Opuntia is a still more difficult genus, and mistakes are here most easily made. Many of them 
are as yet very incompletely known; and without being able to compare a great number of 
living specimens in their native state and in all stages of development, it can hardly be [311] 
expected that any one should know beforehand what constitutes the specific characters in 
these plants. I have tried to unite the forms which seemed to justify such a proceeding (see, e. g., 
O. Rafinesquii, here made to comprise quite a suite of forms as subspecies). Still it may be thought 
that a greater reduction was yet desirable; but with our present data this would involve great danger 
of jumbling heterogeneous materials together. Nos. 5 and 7 (of which latter neither flower nor fruit 
is known) can perhaps be united; also 9 and 10, 11 and 12, 13 and 14, 16 and 17, 19 and 20, 
22-24, 25-28, 29 and 30, 31-33, 35-37, 38-40, and 48 and 49, — leaving 31 types, 29 of which are 
indigenous to our territory, and two cultivated. 
GEOGRAPHY OF THE CACTUS REGION OF THE UNITED STATES. 
The localities where our Cacti grow are so little known to those who have not made the 
geography of the West a particular study, or are not familiar with the publications of our Western 
explorers, that it seems necessary to add a few explanatory remarks. 
Texas, as at present organized, is bounded southeasterly by the Gulf of Mexico, into which the 
following rivers mentioned in the foregoing pages empty, following the order from east to west: the 
Brazos, the Colorado with the Llano, the Guadalupe with the Pierdenales and San Antonio, the 
Nueces, and the Rio Grande. The latter forms the southern and southwestern boundary as high up 
as El Paso. On it are the towns of Matamoras (not far from its mouth), Mier, Laredo, and (higher 
up) Presidio del Rio Grande ; then Fort Duncan or Eagle Pass (southwest of which is Santa Rosa, in 
the State of Coahuila). Next comes the mouth of the San Pedro or Devil’s River (a small river, or 
rather torrent, running southward); and not far from it the mouth of the Pecos or Puerco, which 
rises at the north-northwest in the upper parts of New Mexico. Between the mouth of the Pecos 
and El Paso we notice only Presidio del Norte, San Elizario, and a “ cafion” below the latter. The 
valley of the Limpio—a little more to the northward, between the Pecos and El Paso—is a remark- 
able locality ; probably because there porphyritic rocks take the place of the cretaceous formation of 
the more eastern districts. 
Chihuahua is the well-known capital of the Mexican State of the same name, south of El Paso. 
The Canadian River is a southern tributary of the Arkansas, running eastwardly very [312] 
nearly under the 35th degree of latitude, and bounding on the north the elevated plains 
known as the Llano Estacado, in the northwestern parts of Texas and the adjoining regions of 
New Mexico. 
