gO SOR AES SESE I SE TE i FS EL SP SO EEA EE Ee 
SCIENCE IN THE PLANT WORLD 
on his return the next morning. It took several 
nocturnal visits to unravel the mystery and 
discover that the flowers folded themselves 
and retired so adroitly into the surrounding 
foliage each evening that they were completely 
hidden. 
The Acacia is a plant which closes up at 
night; the same phenomenon is very striking 
in the Oxalis. The common Bean sleeps stand- 
ing: that is, its leaves close upward instead of 
downward. The little blue Veronica flower, 
so strikingly brilliant and attractive in the day- 
time, tucks itself in so snugly at bedtime that 
it becomes quite inconspicous. A Marigold 
called Calendula Pluvialis even contracts its 
corolla every time the sun is veiled by a pas- 
sing cloud. ‘These sleep movements all have 
a scientific purpose. Their main object, just 
as in animals, is to reduce bodily activities to 
a low ebb and so to give the plant a chance to 
recuperate for another day’s efforts. The con- 
traction of all surfaces cuts down the radiation 
of heat and moisture and presents less resis- 
tance to outside elements. The plant is in a 
quiescent, somnolent state. 
[125] 
