THE STUDY OF NATURAL HISTOTIY. 799 
exceed one thousand four Imndred. Theophrastus, a Greek Philoso- 
pher, who succeeded Aristotle in his school at Athens, wrote a work, 
entitled "The History of Plants/' in which about five hundred dif- 
ferent plants are mentioned. Dioscorides, a physician and botanist 
in the time of Nero, being nearly three hundred years after Theo- 
phrastus, describes about six hundred different plants ; Pliny the 
elder, who lived about the same time, in his voluminous woi"k, enti- 
tled " The History of the World," gives descriptions of one thousand 
different species of plants. The interesting study seems to have been 
but little cultivated for many centuries, posterior to the time of Pli- 
ny ; for Bock or Bone, a german, generally known by the name of 
Trague, in 1532, published a History of Plants, in which he des- 
cribes only about eight hundred species. It is from the Western 
hemisphere, we have obtained so many choice and elegant speci- 
mens of exotic plants ; the vegetable productions of America, exceed 
in point of number and luxuriance, those of Europe. In North 
America, for instance, the number of lofty trees is far greater than 
in Europe. In the former country, there are one hundred and thirty- 
seven species of trees, whose trunks exceed the height of thirty feet, 
while in Europe there are but about forty-five species. 
There is no subject in Botany more admirable, than a contrivance 
visible in many plants, to take advantage of good weather, and to 
protect themselves from bad. They open and close their flowers, 
and leaves, under differ^ent circumstances. Some open to receive the 
I'ain, others close to avoid it ; some close before sun-set, others after. 
The petals of many flowers expand in the sun, but contract at night, 
or on the approach of rain. 
Plants, when forced from their natural position, are endowed with 
the power to restore themselves. A hop plant twisting round a stick, 
directs its course from south to west as the sun does. Untwist it, 
and tie it in the opposite direction, it dies. Leave it loose in the 
wrong direction, and it will recover itself in a single night. Twist 
the branch of a tree so as to invert its leaves, fix it in that position ; 
if left in any degree loose, it untwists itself gradually, till the leaves 
are restored to their natural position. What better can an animal 
do for its welfare ? The root of a tree meeting with a ditch in its 
progress, is laid open to the air. What follows ? It alters its course 
like a rational being, dips into the ground, sun-ounds the ditch, rises 
on the opposite side to its wonted distance from the surface, and 
thence proceeds in its original direction. Lay a wet sponge near a 
root laid open to the air, the root will direct its course to the sponge. 
Change the place of the sponge, the root varies its dii'ection. Thrust 
