1898 ] FLORA OF LOWER SONORAN AND ARID ZONES 147 
(1) Involucral bracts with recurved hooks ; stems fragile at joints: 
Chorizanthe, Oxytheca, Lastarriza. 
(2) The whole plant beset with barbed hairs; stems very brittle: 
Loasacez. 
(3) Rough or spiny projections on calyx or carpels: Tribulus, 
Kallistrcemia, some Cryptanthes, Froelichia. 
(4) Calyx with sharp, sometimes recurved stiff hairs; fruits easily 
falling away ; many Borrag.- Eritrichiez. 
(5) Carpels flat, with hooked sete: Pectocarya. 
(6) Fruits adhering by woolly covering: Gossypianthus, Freelichia, 
Gomphrena. 
For most species, then, the distribution and relationships in 
the two zones are such as can be accounted for from data that 
are reasonably well established. The element which remains 
rests upon very much the same basis of speculation as the rela- 
tion of New World to Old World Zygophyllacee, or Aus- 
tralian and South American Chenopodiacee, or, indeed, the 
relation of the great salt desert regions of the world to each 
other. 
UNIVERSITY OF TEXAS. 
