PLANTS THAT GO TO SLEEP 161 
The goat’s-beard, sometimes known as “Go-to-bed- 
at-noon,” is so named on acount of its strange 
custom of closing at that hour. The crocus often 
closes up by noontime; and the oxalis will fall to 
sleep, like a tired child, at various times of the day, 
especially if the sun is shining on it; while other 
plants, like the moonflower, the datura, and the 
night-blooming cereus, sleep practically through- 
out the entire day and come forth at night in all 
their beauty! 
These habits of opening and closing at different 
times of the day and night are not only a protec- 
tion against cold and heat, but also an assurance 
that the plant will be ready to receive its welcome 
guest, the pollen-bearmg insect, whether he be a 
toiler of the night or of the day; for instance, the 
datura is visited only by insects of the night, and 
if, for any reason, it opened its blossoms in the 
day, it would possibly be neglected, and its flowers 
left unfertilised. 
But plants require not only their daily sleep and 
rest; they must have longer periods of undisturbed 
quietude; in other words, they require vacations. 
So plants hibernate, just as the chipmunk, the clever 
arctic fox, and the arctic bear hibernate when the 
cold weather approaches. And they are quite as 
cunning and ingenious in providing for themselves 
