574 
*Smelowskia calycina. 
i r 
iola. 
Heuchera cylindrica. 
*Saxifraga adscendens. 
n. » punctata. 
*Geum Rossü. 
*Potentilla dissecta. 
Astragalus platytropis. 
Part IV. Chapter 3. 
Astragalus tegetarius. 
> calycosus. 
*Oxytropis campestris. 
*Vaceinium caespitosum. 
*Kalmia glauca 
*Pirola rotundifolia 
FA 
ndrosace septentrionale. 
*Primula Parryi. 
*Swertia perennis. 
*Gentiana Parryi 
*Polemonium confertum, 
*Antennaria alpina. 
> carpathica. 
*Erigeron compositus. 
* 
> salsuginosus,. 
*Solidago virgaurea. 
*Aster glacialis. 
*Senecio amplectens. 
canus. 
Chaenactis Douglasii?). 
ıryi. 
*Phlox caespitosa. | 
aboriginorum. 
C. Arizona- New Mexico District. 
This district is characterized by the inclusion of such deserts, as the 
Painted Desert in northern Arizona, the Tularosa Desert in New Mexico and 
others stretching eastward to join the plains of western Texas and south- 
ward into the deserts of Chihuahua in Mexico. 
This district lies southeast of the grand Canyon of the Colorado River. 
It embraces several mountain ranges which may be said on the higher sum- 
mits to have a typic Rocky Mountain flora, which for purposes of convenience 
will be treated in connection with the consideration of the flora of the New 
Mexico-Arizona District. 
Looking from a mountain top the traveller is impressed with the wonder- 
ful diversification of the desert landscape. Here he sees a vast flat of alkali; 
there an area of vulcanism where the lava has overflowed square miles of 
country. Elsewhere are arid hillsides and isolated table-lands, or mesas glowing 
with every conceivable shade of color. While in the distance rise mountain 
peaks that are during a large part of the year snow-copped. Elsewhere sand 
. dunes are seen with characteristic wet dune bottoms, while progress across the 3 
country is blocked by deep canyons. The physiognomy of the vegetation 
impresses the botanist as much as the physiography for low mesquite trees 
abound with low thomy shrubs, yucca-like plants dotted over the arid plains, 
while the oak and pinon belts.of the lower mountain slopes suggest a shrub 
steppe or a Mediterranean oak or laurineous forest where sclerophyllous trees ä 
are the prevailing type. — 
e plants are modified structurally and seasonally to a desert climate. 
Their root systems are either deeply placed (Prosopis juliflora), or supef 
ficially placed and strongly branched (Cereus giganteus); their leaves are 
reduced in size; they have water-storing stems; their leaves are leathery 
or succulent with thick cuticle, sunken stomata and other protective devices, = : 
while their rapidity of development after showers of rain is astonishing. We 
have as a result of this two kinds of desert plants existing side by side, 
viz., typic desert xerophytes and desert mesophytes which develop during the; 
ee ir 
RR 
EM, 
1) ENGLER, A.: Die pflanzengeographische Gliederung Nordamerikas: 87. 
