ee ot Oem: aes chal eats EL DE 
1898 } FLORA OF LOWER SONORAN AND ARID ZONES 137 
In the above will be noted (1) the greater number of com- 
mon genera in Argentine and the Lower Sonoran zone ; (2) that 
most species have no special mechanical devices for seed trans- 
portation. 
BORRAGINOIDEZ-ERITRICHIES. 
The Borraginoidez-Eritrichiez of the Pflanzenfamilien include 
seventeen genera, of which two, Lappula and Eritrichium, possess 
a broad distribution in the temperate zone of both hemispheres. 
Seven genera are chiefly E. Asiatic. Eight other genera occur 
in western North America, of which four recur in Chili. The 
geographical center of this group would appear to have been 
eastern Asia. From here the migration would have been along 
the chain of islands, Aleutian, etc., joining Asia and America, 
or by Behring strait and along the continental axis to extra- 
tropical South America; and hence the group would fall in with 
the boreal element represented in the Andes of Bolivia, Peru, 
and Chili. But the group has attained a distinct development 
in the Lower Sonoran zone of North America, and in the 
Atacama-Chilian arid zone, and for that reason is discussed here 
in some detail. It is to be noted that at one time or another, 
almost all of the west American development of Borraginoidee- 
Eritrichiex (both north and south) has been referred to the 
genus Eritrichium (excepting, of course, Amsinckia), and this 
fact may be made important in interpreting the present condition 
of the group in the western hemisphere. The Eritrichium type 
still prevails in a few species, and these are notable for being 
high mountain forms distributed along the continental axis from 
Alaska to southern Chili, with a considerable interruption from 
southern Mexico to Ecuador, while the forms referred to distinct 
genera represent apparently the variations resulting from the 
Occupancy of a vast arid tract. 
In the Synoptical Flora (191-199, ed. 1), Asa Gray included 
allof North American Borraginoidex-Eritrichiex under Eritrich- 
ium, Echidiocarya, and Amsinckia. In Proc. Amer. Acad. 20 : 264, 
and Syn. F/. Suppl. 423-433 (ed. 2), the two latter are retained, 
