THE AMERICAN BOTANIST. 
7 
at the same time sweeping through an arc. To see this 
movement one must have the plant either in a hot, moist 
cHmate — or under similar artificial conditions in a hot-house. 
The writer has frequently observed them in the fine con- 
servatories of the Harvard Botanic Garden. Gray com- 
pares the jerking movements to those of the second hand 
of a clock, but without the clock's regularit}^ He writes 
"Stopping for a time, they again more briskly, always 
resting for a while in some part of their course, commonly 
at the highest and lowest points, and starting again without 
apparent cause, seemingly of their own will. The move- 
ment is not simply up and down, but the end of the leaflet 
sweeps more or less of a circuit. It is not set in motion 
by a touch, but begins, goes on, and stops of itself." 
One is completely lost — at least the writer is — in trying 
to solve the riddle of this movement. But let us revert to 
"the sleep of plants" in their more familiar aspects. If one 
seats himself on a summer afternoon about four o'clock, 
in a large garden, or perhaps even in the woods, and ob- 
serves what happens as the afternoon wxars on, will, to his 
surprise, find extraordinary changes taking place in the ap- 
pearance of the surrounding vegetation. In a botanic gar- 
den these alterations are very striking. I have fancied that 
at times one can even hear a little "click" as the leaves meet 
in closing. 
Early in this garden session, all the leaves will be lev^l 
and expanded, except, of course, such as are naturally ver- 
tical, like the Iris and most grasses. The compound leaves, 
one and all, will be spread open. If it should happen that 
our observer should doze himself for an hour or so, and 
then suddenly awake, he will not fail to note that something 
has happened. 
Indeed, a transformation scene is being enacted. A 
lot of the leaves have closed — others are closing — some even 
