646 Part IV. Chapter 5. 
In the absence of a detailed description‘) of the plants found in these for- 
mations, it has been found expedient to mention the plants which grow in this 
great territory by grouping them into divisions, such as, leguminous plants, 
cactaceous and compositous plants. All of the plants of these orders, 
as well as those ofthe Gramineae and Liliaceae, furnish plants which have 
adapted themselves to the dry soil and other desert conditions. Many of them, 
especially the yuccas, agaves and cacti have assumed a morphologic cha- 
racter which is an expression of their desert habitats. 
The trees of the desert mountain ranges and dry canyons of Chihuahua are limited to a 
few species: Pinus chihuahuana, Quercus Emoryi, Q. grisea (= Q. undulata), Q. oblongifolia, 
Fraxinus cuspidata and Juniperus occidentalis var. conjugens. These species grow on thedry 
mountain ranges which rise from the plains to an elevation of 6,000 to 8,000 feet. 
The Cactaceae?) are represented by following important species: 
Melocactus ferox. Mamillaria scolymoides. Echinocactus rhodophthal- 
Mamillaria anguinea. » sphaerotricha. 
» icolor. Echinocactus coptogonus. » tricuspidatus 
. centricirrha. » hexa&drophorus. (=E. phylla- 
> conoidea. > helophorus. canthus). 
> conopsea. > hexaädrus, » uncinatus. 
> erebrispina. > hystrichacan- > ingens 
> recta, Opuntia rufida. 
, formosa. > latispinus (= E. > chottii 
> hexacantha. cornigerus). > _ tunicata. 
» hystrix. > longi tus, » gari 
> implexicoma. > macrodiscus, >» _ leptocaulis. 
f > .  longimamma. » myriostigma. Cereus (Echinocereus) pecti- 
> raphidacantha. » pectiniferus. atus, 
> Scheidweileriana. » quadrinatus, >»  geometrizans (s, Fig.31). 
Among the leguminous plants characteristic of the region are Indigofera Lindheimeriana, 
Peteria scoparia, Astragalus diphacus, A. coriaceus, A. le tocarpus, A. parvus, Hosackia puberula, 
Lupinus canus and Sesbania longifolia, Crotalaria sagittalis, Glycyrrhiza lepidota, Prosopis pubes- 
cens and many other species of the genera Petalostemon, Dalea, Tephrosia (— Cracca), Astra- 
galus, Galactia, Rhynchosia, Hoffmanseggia, Parkinsonia, Cassia, Desmanthus, Mimosa, Acacia, 
Calliandra and Pithecolobium. 
The species of the genus Yucca, which reach the size of small trees and are of American 
desert origin (see ante page 298), find their most luxuriant development and center of distribution 
in the Chihuahuan desert region. The following yuccas are limited to this region: Y, Treculeana, 
Y. australis, Y. valida, Y. rigida, Y. rostrata, Y. radiosa, Y. macrocarpa, Hesperalo@ funifera 3). 
Some of the species of Agave of this desert region are Agave applanata, A. asperrima, A. Brau- 
niana, A. (Manfreda) guttata, A. Humboldtiana, A. Peacockii, A, Smithiana, A. Wislizeni and A. 
zylonacantha4). 
T) KirKwooD, J. E.: Desert Scenes in Zacatecas, Pop. Sei. Month. LXXV: 435—451. 
2) The names in Hemsley’s Biologia and Schumann’s Monograph have been retained although 
as previously stated the entire family has been reorganized. 
3) RAMIREZ, Jos£: La Vegetacion de Mexico, 1899 Page 115; Trelease, The Yucceae. 
Thirteenth Annual Report (1902) Missouri Botanical Garden, pp. 27—133. 
4) SEGURA, Jos£ C. y CORDERO, MANvEL D.: Resena sobre el Cultivo de algunas Plantas 
Industriales. Mexico 1884 El. Maguey PP- 207—277. 
