8 
THE AMERICAN BOTANIST. 
with a degree of suddeness, and this lessening of exposed 
surfaces causes a manifest difference in the appearance of 
the whole landscape. 
Among plants in which the phenomenon of "sleep" 
is very marked, I will mention the sorrels or oxalids, the 
clovers and their congeners, like melilot, lucerne, all the 
locusts, and many peas and beans. Then, too, we have the 
really very sensitive species of Cassia, the nic titans and 
chamaecrista, very pretty plants of the pea family with 
rather large, yellow, almost regular, handsome flowers. 
The mere plucking of these dehcate plants is enough to 
induce almost immediate movement of the numerous pairs 
of leaflets, which close upon each other till the whole leaf 
droops like a ribbon. It has a very tired look, and the 
sleep continues for some time after the disturb- 
ing influence has been withdrawn. Very much more start- 
ling is the movement in the true sensitive plant of hot- 
houses, the Mimosa pudica. Listen to what Gray says of 
it: 
"In the well-known sensitive plant (Mimosa pudica) 
the foliage quickly changes its position when touched, ap- 
pearing to shrink away from the hand. It makes three 
movements. First the numerous leaflets close in pairs, 
bringing their upper faces together and also inclining for- 
ward; then the four branches of the leaf-stalk, which here 
outspread like the rays of a fan, approach each other; at the 
same time the main leaf-stalk turns downward, bending at 
its joint with the stem. So the leaf closes and seemingly 
collapses at the touch. In a short time, if left to itself, it 
slowly recovers the former outspreading position." 
This plant responds quickly to the rays of a burning 
glass directed upon it, and can be put to sleep by ether or 
chloroform, awaking again, if the dose is not enough to kill. 
Of course it is manifest that in this shrinking, the plant ex- 
