39 
shows that they are manifestily variably localized forms of recent 
origin and with no Mexican connection. Take for example the species 
of the Navajo Basin. The exclusive species are A. Coltoni and its 
forms (though this occurs sporadically even as far as Pioche), de- 
tritalis, Duchesnensis, Kaibensis, Episcopus, forms of junceus and 
montanus, sesquiflorus, Wingatensis. The Inflati have lutosus, puben- 
tissimus, Wetherilli, while subcinereus, Wardi and megacarpus are 
nearly local, and only Geyeri, lentiginosus, -pictus, oophorus and 
rabulonum are at all widely distributed. Of the Preussií ampullarius, 
¿sciepiadoides, Pattersoni sabulosus and Preussii are most local 
and only Pattersoni passes its borders a little, and Preussii only 
has any considerable distribution in the the Great Basin. A. Mortoni 
is generally distributed, A. Brandegei and straturensis are local. 
These are not of the Preussii. Of the Argophylli A. cymboides, des- 
peratus and Musiniensis are local, pygmeeus nearly so extends to the 
Mogollons, while Utahensis and Purshii cover the region to the 
Sierras. Of the Mollissimi A. Bigelovii alone extends through to 
eastern Nevada and southward. Of the Ocreati every species is local 
except confertiflorus which runs up into the Green River Basin. Of 
the Bisulcati A. Osterhouti only is local, and Haydenianus extends . 
only to central Nevada. Of the Lonchocarpi the single type species 
extends only to central Nevada, Of the Hamosi A. calycosus extends 
throughout the Great Plateau. Out of the forty seven species twenty 
six are local and half the rest are only slightly extra-limital, and only 
two or three go to the Arizona deserts. 
Of the Green River Basin (to the north of the Uintas) there is one 
exclusive species A. Grayi. : 
The species of the Great Basin show similiar localization. Out of 
its thirty nine species and about twenty varieties A. serpens of the 
.Inflati is local; of the Podo-sclerocarpi Casei, pterocapus,tetrapterus, 
‘Serenoi, Toanus are local; of the Inflati Beckwithii is nearly local. 
Of other groups are forms of arrectus atratus, pinonis, iodantus. P 
malacus, Andersoni are exclusive or nearly so, or abuot fifteen out. 
of forty seven forms, while nearly a dozen more are only a little 
extra-limital. ` 
In the Columbia Basin A. speirocarpus, sclerocarpus, inflexus and 
succumbens are local out of fourteen species. 
In the Rio Grande region only Feensis and oocalycis are local. 
due to lack of barriers. 
In the Mogollon plateau region the Homalobi have A. Gilensis 
as an exclusive; the Inflati have nutans, allochrous, Palmeri, Thur- 
beri; the Lotiflori A. accumbens. Other groups have Cobrensis, re- 
curvus, remulcus, Phoenicis, funereus, coccineus, ensiformis, Arizonicus. 
The Sierra Madre region has scalaris and Goldmani as exclusives. 
In the Plains region the only exclusives are lotiflorus, anisus, 
pectinatus and parviflorus. 
The eastren region has villosus, Tennesseensis, distortus and 
possibly glaber as exclusives. ; 
The Sierra region has few exclusives such as bicristatus, pachypus, 
Bernardinus, with Andersoni and Gibbsii nearly so. The total species 
in this life zone are 152 or 35 per cent of the whole. 
This life zone ocupying the center of the Great Plateau has barely 
got a footing in the center of the Columbia Basin and extends but 
little north of Pueblo Colorado. At the south it has been exterminated 
at all elevations below 3,000 ft. in the Utah-Nevada region, and at 
all elevations below 4000 ft. in the Arizona region, the Tropical taking 
its place. This has resulted in broad fringes around nearly all the 
mountain ranges at the south and limited by live oaks. 
