1894.) Comparative Histology of Pulvini. 481 
mon term, using the same for two very different structures. 
Burdon-Sanderson® speaks of the organs as ‘‘ motor organs.” 
Ido not know whether it was a mere accident on his part or 
a premeditated change, but ashe states no reason for so doing, 
Ijudge that it was the former. It is, however, a happy sug- 
gestion and therefore instead of the term which .is in such 
common use, motile organ, I propose to adopt the term 
motor organ for those structures whose curvatures set in mo- 
tion other passive parts. In electro-mechanics it is the motor 
that drives the machinery. Now the motor organ, like the 
electric motor, causes other structures to move, the leaf being 
Passive and taking whatever position is necessitated by the 
curvatures of the motor organ. This, then, seems to me to 
ean especially good term, and in adopting it we shall avoid 
confusion in the minds of those who do not command a view 
of the whole subject. 
Method and material. 
: The material for the work on this subject was collected dur- 
ing the summer of 1893, in the months of June, July and 
August. At the same time that the collection of material — 
Was made the positions of the leaves were noted. A small 
fase containing bottles of Flemming’s fluid was carried into 
the field; the specimens of motor organs were snipped off 
with a pair of scissors, leaving only such additional parts of * 
leaves, petioles and axes as were necessary for examination, 
4nd placed immediately in the fixing fluid. The plants were 
_‘Usited during the day, the position of the leaflets noted, and 
_ Material collected. They were again visited about dark, and 
Specimens of the organs in their nocturnal position were ob- 
fined; at the same time a record of the position of the leaf- 
&ts was made. Some leaves were slow in assuming their noc- 
_turnal position, and in those cases it was necessary to visit 
_ Nations which are possible in studying a plant out of its nat 
_“alhabitat. On the other hand the observations required 
“nsiderable time and trouble because some of the species 
f= local, and it was n ecessary to go toa distance in order 
| btain specimens from them. 
: i. Specimens of the motor organs, 
_~"™Ming’s fluid as soon as removed, were 
which were placed in 
allowed to remain 
a et ° . 1882, 
: Burdon-Sanderson: The Excitability of Plants. Nature. 26: 353, 483 
