PREFACE. Xi 
No botanist, even if in danger of starving in a 
wilderness, would indulge his hunger on a root or 
fruit taken from an unknown plant of the nat- 
ural order Luride, of the Multisilique, or the wm- 
belliferous aquatics. On the contrary, he would 
not feel a moment’s hesitation in regard to any of 
the Gramina, the fruit of the Pomacew, and several 
other natural families of plants, which are known 
to be uniformly innocent in their effects. —— 
The sensible properties of plants afford another 
clue to their influence on the human system. It 
is true, that observations derived from this source 
will not serve us in forming very minute distine- 
tions. ‘They are, however, almost always adequate 
in vegetable productions, to enable us to distin- 
guish what is innocent and salubrious, from what 
is noxious and virulent. The brute creation de- 
pend wholly upon the powers of sense in selecting 
their food, and this reliance does not often betray 
them. In regard to mankind it almost uniformly 
happens, that what is sweet, delicious, or aromat- 
ic, proves nutritive or salutary; while on the oth- 
er hand, vegetable poisons are nauseous, acrid, 
and disgusting. It has been observed, that it 
would have been a sort of treachery in nature to 
have made it otherwise. Considering the univer- 
sal dissemination of poisonous plants, and the 
