6 
THE AMERICAN BOTANIST. 
When it is known that there are extant over seven hundred 
species of cacti, the folly of any attempt, in the scope of so brief 
an article as this, to give a list even of the families, must be at once 
apparent. My only effort, then, shall be to give a brief idea 
of the more common of our wild forms, which are to be met with 
almost from seashore to mountain top. 
According to the best authorities, the cactus was unknown to 
the Old World prior to the discovery of America by Columbus, 
though now it is as plentiful along the shores of the Mediter- 
ranean and in other arid portions of Asia and Africa as it ever 
was in our own deserts. Like camels, ostriches and other forms 
of desert life^ the cactus has developed within itself — by means oi 
its fleshy leaves — a perfect storehouse of nutriment, capable of 
withstanding the rigors of drought froin one rainy season to an- 
other. 
What we call the 'leaves" of the cactus in reality correspond 
to the trunk and branches of other shrubs, while the leaves them- 
selves have been retarded until they are degenerated into the 
spines and thorns which prick us when we attempt any undue fa- 
miliarity. 
All plants grown in arid places tend to develop very thick, 
succulent stems, having little or no leaves, but a very thick skin to 
prevent the absorption of their life juices by evaporation. A very 
good instance of this is to be found in the common "ice plant" 
which grows so thickly along our beaches, just above high-water 
mark. 
Further, as every plant must absorb its carbon from the air in 
the form of a gas, it follows that plants of this class tend to pre- 
sent the greatest possible expanse of surface to that air, and, on 
the other hand, have widely-spreading roots, set shallow in the 
ground, so as to get the greatest possible amount of nutriment and 
moisture from the earth. Lastly, as a super-fine product of the 
evolution of a species, we note that the cactus presents (as I have 
said before) its true leaves in the form of spines for the sole pur- 
pose of protecting itself from such animals as, wandering in desert 
regions, would seek to eat it. Some cultivated forms of cacti 
