218 BOTANICAL GAZETTE [SEPTEMBER 
tion of the main range. These are locally known as the Mojave 
and the Colorado Deserts.” These two subareas have many 
plants which are common to both, but each possesses also a dis- 
tinctive flora. These characteristics, so far as they relate to 
genera, are exhibited in the subjoined table. 
GENERA PECULIAR TO THE DESERT AREA. 
CoLorapo SUBAREA 
MojAvE SUBAREA 
BoTH SUBAREAS 
Northeastern Element 
Northeastern Element 
Northeastern Element 
Astephanus —— Anisocoma 
Amsoni Grayia 
Southeastern Element Atrichosers Piptocalyx 
*Bou Tricardia 
: Piomuaile 
*Argythamnia *EUROTIA Southeastern Element 
A. Forestiera 
*Beloperone Glossopetalon Acamptopappus 
Pie avila Glyptopleura Achyronichia 
Caltiandra KocuHIA Baileya 
*Cercidium GODESMIA Bernardi 
loris Monoptilon Cladothrix 
*Condalia Phellopterus HILARIA 
Vicoria URSHIA *IKRAMERIA 
*Fagonia STANLEYA *LARREA 
ane =e ee ee 
*Horsfordia sms ia THM sae 
*Hoffmanseggia Ax richoptilium 
*HOFMEISTERIA 
*HYPTIS : Southeastern Element Indefinite 
*Leptochloa : 
Martyni Canotia Calycoseris 
*Olneya Coleogyne Chylisma 
a gaa Fallugia *Dalea 
ee Psilactis *Ephedra 
Peucephyllum PETALONYX 
*Palafoxia Psathyrotes 
*Porophyllum Sphaeralcea 
Sesbania 
*Triodia 
Tribulus 
Trixis 
*W ashingtonia 
It appears by this table that the desert genera fall into three 
nearly equal groups: namely, those which are found only in one 
or the other of the two subareas, and those which occur in both 
22 The region bordering the Colorado River is too little known to permit exact 
statements regarding it. There are reasons for believing that the Colorado subarea 
— oo. the interval between the river and the eastern slope of the Providence 
Moun 
