Southern extension of’ North American flora. 337 
probability a north-south distribution of xerophilous mountain elements was 
much easier at some earlier period than at present. Illustrations include 
xerophilous ferns of 6 genera, many of which range from west Texas, New 
Mexico, Arizona, etc., to Mexico, Guatemala and in the South American 
Andes to Chili. The illustrations afforded by the Leguminosae include 
such genera, as Asiragalus, Dalea, Lathyrus, Lupinus, Vicia. Other orders 
represented are Rosaceae-Quillajeae; Compositae-Astereae, Compositae-Solida- 
gineae; Cactaceae; Boraginaceae-Eritricheae. The genus Gilia (Fig. 21) is 
included as well as many others. Gilia includes some eighty North American 
species and about fifteen Chilian species. 
Western North America. Chili. 
Gilia laeiniata Ruiz & Pav. 
> multicaulis Benth. | Gilia laciniata Ruiz & Pav. 
> achillaefolia Benth, 
a z » crassifolia Benth. 
> ıinconspicua Sweet (= G. parviflora > - copiapina Phil, 
ee. » longifolia. 
> involucrata (incl. 
> intertexta Stend. >» Navarretia Steud., and 
» eryngioides Lehm.). 
> minima A. Gray. dwarf forms of G. involucrata in Chili. 
> pusilla Benth. Gilia pusilla Benth. 
Collomia linearis Nutt. Collomia cocceinea Lehm. 
Polemonium antarcticum Griseb. (= P. micran- 
thum Benth.). 
Polemonium micranthum Benth. 
The most extreme xerophytes and halophytes occupying the most arid 
deserts of both North and South America in the extra-tropic regions, and 
generally unrepresented in the moist tropic and high mountain areas between. 
Such are the Mimoseae, Prosopis $ Strombocarpa with 3 species in Argentine; 
3 Species in west Texas, north Mexico and westward; $ Algarobia with 19 species 
mostly in Argentine; but including Prosopis juliflora of wide range; Polygonaceae- 
Eriogoneae with eleven genera characteristic of southern California and adjacent 
arid regions (except some Eriogonum) and the peculiar subgenus Chorizan- 
thopsis of Chorizanthe, endemic in Chili, and three species common to both 
@ones, namely, Oxytheca dendroidea, Chorisanthe commissuralis and Lastarrıaca 
chilensis, all originally from the Californian region; Frankeniaceae with the 
very distinet Ayankemia Famesii of the west Texas region, F. Palmeri of the 
Southern California region, F. triandra of the Puna region six nearly allied 
Chilian species, one of which is in California and Arizona, and Niederleinia 
Juniperoides of the Argentine salt steppes, more nearly related to the lower 
Sonoran than to the Chilian species. The largest genus of Loasaceae fur- 
Nishes many desert species for the Atacama and Argentine deserts, and while 
developed mostly in these regions and in the Andes, some species push north 
Harshberger, Survey N.-America, 22 
