104 BOTANICAL GAZETTE | AUGUST 
the Chisos and other mountains in the Great Bend up to 6000 
feet, 
Of these several provinces, each of which possesses distinct- 
ive floral or physiological conditions, the Rio Grande plain is 
clearly related to the tropical and the subtropical in its prepon- 
Fic. 2.— Geology of the greater Texas region; 7, Older Granites; 2, Palaeozoic 
and Mesozoic; 7,Cambrian and Silurian; 4, Carboniferous; 5, Permian; 6, Jurassic ; 
7, Lower Cretaceous; 8, Upper Crnekeeoun: g, Non-marine Tertiary; 70, Marine 
Eocene; 77, Coast Neocene; 72, Later i igneous.— From 1 Sis Phys. Geog. Texas. 
derance of Mimoseae and Caesalpineae, of Rhamneae, Zygophyl- 
laceae, Rutaceae, Simarubaceae, Malvaceae, Euphorbiaceae, 
Nyctaginaceae, and similar groups. The central plains of the 
north, on the contrary, possess a minimum of these groups, but 
more which are peculiar or common to the central prairie plains 
of Kansas, Missouri, Indian Territory, and Oklahoma, such as 
Compositae (certain subfamilies), Papilionaceae, Onagraceae, 
and others. The identity of plant formations, however, as 
