660 Part IV. Chapter 6. 
Treculeana, Tillandsia Baileyi, Jatropha macrorhiza, J. multifida , Malpighia glabra and Solanum 
triquetrum®). Sabal mexicana is fonnd in limited numbers in the Brownsville neighborhood, 
Mesquite Facies or Association of Prosopis juliflora in the Rio Grande plain 
occupies the level areas of fine compact silty debris. It is often associated with Opuntia 
Lindheimeri. Similar *mesquite flats” as they are commonly called, are found in similar situa- 
tions in the hotter portions of Texas but the species also occupy the black prairie soils in some 
areas, From San Antonio southeastward is a vast mesquite forest with trees ten to fifteen feet 
tall and in the lower Rio Grande valley individual trees attain a height of thirty-five feet and a 
diameter of two feet. 
The Acacia Farnesiana Facies, according to BrAy, prevails on the low moister 
coast prairie clays. The species is more limited than the mesquite in both moisture and tem- 
perature requirements. Its spread has been on the coast prairie as far east as Galveston. — The 
Acacia amentacea Facies is the prevalent one in the northern half of the Rio Grande 
plain. Constituting sixty to seventy-five per cent of the shrubby vegetation on many thousands 
of acres, it is known as the “black chaparral”. The Acacia Wrightii Facies is especially 
prevalent as an open one on grass plains in vor northern part of the Rio Grande region between 
the Nueces and Medina rivers. he Huajillo Facies (Acacia Berlandieri) occupies 
the basalt ridges and cones extending east er west along the northern border of the region. 
Farther southeast, it has been noted on coarse gravelly ridges denuded of finer sediment and the 
trees scarcely exceed three or four feet in height. Parkinsonia texana, found on the coarse 
gravelly slopes near Eagle se is an habitually procumbent or straggling shrub which, while 
occupying the ground fully, is ry diffuse covering. — The more arid parts of the Rio Grande 
country especially within ei ae of the river on both the Texan and Mexican sides are 
occupied by a solid mass of Leucophyllum texanum which on account of a hairy felt cove- 
ring the leaves gives it a light tone conspicuous to the uninitiated eye. 
Mixed Coast Chaparral Formation. From the mouth of the Rio Grande 
to Corpus Christi, the coast is low, mostly bare and unattractive. The trees 
which occur here, are Prosopis juliflora, Acacia farnesiana, A. flexicaulis, Par- 
kinsonia aculeata, Diospyros texana, Celtis mississippiensis var. reticulata. The 
scrubby chaparral?) extending from the shore inward for several miles, 
consists mostly of Prosopis jJuliflora, Diospyros texana, Acacia amentacea, Con- 
dalia, Castela, Zanthoxylum, Lippia lycioides, Lantana camara, Berberis tri- 
Jeliolata, while the vines comprise Anredera, Vitis, Serjania, Maximowiczia. 
The chaparral, which we have outlined as characteristic for southern Texas, 
extends southward along the coastal plain of Mexico. It reaches a consid- 
erable width, according to my observations, west of Tampico in the low flat, 
hot country, but owing to absence of information its exact extent cannot be 
given for other parts of eastern coastal Mexico. Upon reaching Yucatan, 
however, this formation which forms such a conspicuous part of the vegetation 
in nearly all the arid regions of the earth (Argentina and Chili, central South 
Africa, Australia, etc.) spreads out and occupies the country to the ex- 
clusion of most other vegetation. The arboreal elements which comprise the 
scrub which covers most of Yucatan are -leguminous, according to HEILPRIN ’) 
and SELER. 
ı) BAıLey, V.: see Bibliogr. p. 75. 
2) Havarp, Dr. V.: Report on the Flora of western and southern Texas. Proceedings U. $. 
National Museum VIII. No. 29. 1885: 
3) Heırprın, A.: Flora of northern Yucatan: see Bibliogr, p. 83. — SELER, 1. c. 
