D2 
boss Ale trunks:in a burned over forest, there is none so inter- 
esting or inion as the Joshua and the Yuccas, of which there are 
many s. They stand out in the desert like scarcecrows with 
their soon bayonet leaves, sometimes three feet long, sticking out 
in swabs at the ends of the stems, or like needles 1n a pincushion 
from. the napa as though protesting mutely at be:ng compelled 
to exist in such a region as that. These descendants of the old 
Tropical flora are few in proportion to the main vegetation, but 
are quite different from. the typical desert flora. 
It is a botanical axiom that the vegetation of a region is in 
matic conditions in w hich they are found. This leads us to the 
subject of life zones. 
LIFE ZONES. 
It has been noticed by all acute travellers, doubtless since the 
beginning of man, that different climates hav e differe nt vegetation. 
This i is particularly noticeable to all mountain climbers within the 
thi 
‘statement of wide circulation and general acceptance was probably 
that of Humboldt about the beginning of the last century. From 
the tops of the lofty mountains of Mexico there dawned upon him 
_ with tremendous force the fact of life zones, as looking from those 
peaks he could see at his feet the Alpine flo ra, and farther down 
at middle elevations, the vast forests and waving plains of the 
Temperate flora, and far down near the sea, the palms, bananas 
and oranges of the Tropical flora; This led him to classify vege- 
tation into Tierra fria, Tierra temperada, and Tierra caliente. 
This same idea was further expanded when applied to the globe 
as a whole, and has received universal acceptance, into the Tropi- 
cal, Temperate, and Frigid life sae the fundamental idea under- 
lying it-all being that of tempera From a botanical point of 
view this classification has one Jecaces of error, as is shown by 
an: goatedige study of the vegetation, and that is, the Frigid does 
not deserve to he classed as a life zone, because its plant life dif- 
fees but: little es that of the Temperate, though the physical and 
visible effects are very noticeable. There are then but two great 
life zones, the Tropical and the Temperate. An exhaustive ex- 
