OF ARTS AND SCIENCES. 311 



in their native state and in all stages of development, it can hardly 

 be 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. Rafoiesqiiii, 

 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 hetero- 

 geneous 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 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 fore- 

 going 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, Lare- 

 do ; and higher up, Presidio del Rio Grande ; then Fort Duncan or 

 Eagle Pass (southwest of which is Santa Rosa, in the State of Coa- 

 huila) ; 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-north- 

 west 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 " canon " 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. 



