146 BOTANICAL GAZETTE | AUGUST 
opened, and so the xerophytic hosts, which had previously 
found favorable territory for expansion and variation in western 
North America, pressed southward; for example the Sonoran 
Composite, Polemoniacee, Cactacee, Borraginez, etc. These, by 
the agency of birds and mammals, were carried over the equator 
to the extra-tropical regions of Chili, where again they found a 
broad, open territory favorable to a varied development. 
Three important propositions result from the foregoing: 
1. We are carried back to a time when the isolated groups, 
like § Chorizanthopsis and Malvastrum § Phyllanthophora could 
have branched off from the North American stem. 
2. Conditions following the appearance of land along the 
eastern base of the Andes might account for a more general dis- 
tribution of those genera like Frankenia, Niederleinia, Larrea, 
and other Zygophyllacex, Spirostachys, and some other Chenop- 
odiacee, which are now widely separated and genetically dis- 
tinct. 
3. Animals, particularly birds and mammals, have probably 
played a prominent part in the distribution of plants across the 
equatorial and isthmus regions. 
In the following tabulation the devices for securing distribu- 
tion are brought together for a general view : 
I. Adaptation for wind distribution : ; 
1. By winged fruits: Bulnesia, Chitonia, Centrostegia, Pterosteg!a, 
Harfordia, 
2. By light, woolly hairs: Larrea. 
Il. Adaptation for distribution by animals. 
1. Probably by birds. 
(2) As food ; fleshy exocarp: Guajacum, Porlieria. : 
(4) Seeds with mucilaginous covering and elastic coiled slime hairs : 
Gilia, Collomia, F agonia, Peganum. . 
(c) Seeds very small; without special devices for clinging, yet poss!” 
bly adhering to birds’ feet in mud or slime: Frankenia, Spifo- 
Stachys. 
2. Probably by mammals, 
(a) As food; nutritious mesocarp: Prosopis. 
(6) By devices for clinging to wool or hair. 
