INTRODUCTION. 
V 
and tlie one in its effort to ascend perpendicularly, and the other to descend, 
they had formed a perfect spiral. But although the natural tendency of the 
root is downwards, if the soil be dry, and any damp substance be placed 
above, the roots will ascend to reach it. Or, if the shrub or tree has taken 
root upon the side of a precipice, and the soil be somewhat nearer above 
than below, the plant will send a root in a straight line to meet it. In sup- 
port of the above fact, we would cite a singular coincidence, or freak of na- 
ture, fully illustrating the natural instinct of the vegetable creation ; and 
one which, perhaps, may have been witnessed by some of our readers. Upon 
the precipice, or side of the perpendicular rocks of the natural bridge in 
Virginia, are to be seen goodly-sized trees, which first took root in the cre- 
vice of the rock some several feet down from the surface of the earth ; grow- 
ing in this situation untH the trees had exhausted all the nourishment which 
could be obtained in those crevices, and the distance being extremely great 
beneath, they, in seeking for the necessary support of Hfe, sent up numerous 
roots to the rich soil above. The curiosity of many a visitor to this remark- 
able place has been excited in regard to the situation and sustenance of those 
trees ; there they now stand as living monuments in proof of the powerful 
and natural instinct of plants. 
A tree growing from an old wall, or cleft of a rock, will, as soon as it 
has exhausted the surrounding soil, send a stem or root down to the soil be- 
neath ; and Stevens, in his searches am'ong the ruins of Central America, 
found magnificent trees, of extraordinary size and of a great height, living 
upon the very tops of some of the highest walls of the deserted edifice of a 
lost race, which having sent stems down to the soil on each side of the 
wall, and forming by this means a firm support, and being thus, as it were, 
strapped together by living cables, they remain to this day in their full vigor 
and strength. 
The plants in a hot-house do not direct their leaves to the stove in 
quest of heat, nor to the door in quest of air, but to the sun in quest of light. 
Plants in a cellar or dark room struggle towards the light ; plants in an 
area turn the tipper surface of their leaves towards it, and, on the contrary, 
their roots suddenly avoid it. 
The tendril of a vine, or the stem of a creeping plant, never makes any 
turn until it comes in contact with some object around which it can entwine ; 
