Chihuahuan Desert Region, 647 
The order Compositae is represented in the Chihuahuan desert by numerous endemic 
species among which may be counted the following: 
Vernonia liatroides. Bigelovia oppositifolia. Zexmenia gnaphalioides. 
“tevia Berlandieri. Solidago scabrida. Viguiera canescens, 
» elatior. Aster potosinus. Helianthus amplexicaulis, 
>» ranunculoides. Conyza microcephala. Perymenium parvifolium. 
»  stenophylla. Baccharis potosina. ncelia lagascaeformis. 
»  unicristata. Pluchea auriculata. Helianthella mexicana. 
Fleischmannia Schaffneri. »  eamphorata. Verbesina hypoleuca. 
Eupatorium amplifolium. Gnaphalium gracile. Spilanthes bicolor. 
azureum. » oxyphyllum. Dahlia graeilis. 
» scorodonioides. Trigonospermum melampo- osmos diversifolius, 
Schaffneri. dioides, Bidens angustissima. 
Barroetea setosa. Melampodium longicorne. > _ heterophylla. 
Brickellia Coulteri, Parthenium argentatum. Calea albida. 
» diffusa, Aioltheca parthenioides. » elegans. - 
> lanata. Ambrosiaconfertiflora (=Fran- Tridax candidissima. 
» Palmer. seria tenuifolia). Eutetras Palmeri. 
> squamulosa. Tragoceros microglossum. Microspermum nummulariae- 
Gymnosperma scoparium (=G. Philactis longipes. Tagetes Parryi. (folium. 
corymbosum). Zinnia juniperifolia. otula pygmaea, 
Perezia oxylepis, 
Xanthocephalum Benthamia- : 
Sanyitalia acinifolia (= S. pro- >»  rigida. 
cumbens). »  turbina 
Zaluzania mollissima Trixis conferta., 
Senecio praecox. 
m, 
Xanthocephalum _sericocar- 
um. u 
Gutierrezia Berlandieri. ymnolomia multiflora. 
At the southern extremity of the Chihuahuan desert region, as shown in 
the contracted portion in the map, for example in the valleys at Tehuacan, 
the desert vegetation reigns supreme. Here the soil is rocky, mostly limestone. 
According to MACDOUGAL’) the main valley at Tehuacan was u er 
eastern side of the main continental ridge and this and the neighboring valleys 
and slopes are a part of one of the most striking deserts in the eh hir 
xerophilous vegetation offers remarkable features of adaptation and a eye 
The abundance of the Cactaceae rivals or surposses even that of Br ee 
part of Arizona and of Sonora and a half dozen of the species being Pe 
forms, the landscape is highly characterized by them. Cereus (Lemaireocereus) 
Weberi, the “sarambullo” Cereus (Myrtillocactus) geometrizans (see Fig. “e ) 
Cephalocereus (see Fig. 30) macrocephalus, Pilocereus Fulvweps, eg 
and 7etetzo, Escontria Chiotilla, Agave marmorata, together with others er ic 
reach a height and attain a bulk as great or greater, than Cereus FEN 
Of the half dozen species of Zchinocactus (E. grandis, flavescens, ;“ war 
one forms huge mounds of small individuals as much as three yards acr ER 
while Z. grandis reaches the size of the saguaro, Cereus ( ge 
teus. In addition to the cacti, euphorbias, agaves and related forms, —_ 
morning glory (/pomoea spec.) has a soft, thick trunk for storage purposes. 
nn 
!) Journal New York Botanical Garden VII: 4. 
