60 
in actinie and in polypes, and probable amongst the 
infusorial animals. Plants, for the most part, re- 
quire light for the continuance of their well-being. 
Yet some flowers expand at morn and close at noon: 
some expand only at noon; the hemerocallis, the 
ferraria tigridia, &c.: some at eve, as cenothera, Xc.: 
some at or near midnight, as cereus or cactus nocti- 
florus. Most plants, when set in shady. places, turn 
from the perpendicular, and even twist toward the 
light. Yet some, as clavaria hypoxylon, and several 
fungi and truffles, seem wholly to belong to dark- 
ness. 
Sleep. 
The wakefulness and sleep of organized beings is 
a subject so nearly connected with that of their sen- 
sibility to light, that it shall be here briefly noticed. 
It appears to be requisite that nervous or other ex- 
citement from external causes, from light and sound, 
from objects stimulating attention, either agreeably 
or otherwise, should be frequently suspended by 
stillness, by quiescence, by darkness, by sleep: or by 
a state analogous to sleep in plants. It is requisite 
to digestion and assimilation of food, to nutrition, to 
growth in youth, to the preservation of health in 
maturity, to the various changes connected with ab- 
sorption and reproduction. During .such intervals, 
animal activity and intellect are like a bell in a clock 
from which the hammer is forcibly withdrawn by a 
turn of the machinery connected with the index, 
which is pointed at the word sz/ent. Of mammalia, 
