SENSITIVE PLANTS. 
25 
microscope plainly shows that in the former condition the pro- 
toplasm is contracted into a round ball, while in the latter state 
the endochrome is diffused throughout the interior of the cell. 
No general movement of the whole frond is perceptible here, and 
the circumstance is merely alluded to as showing in a marked 
degree the contractile power of the protoplasm, and as offering 
grounds for the conjecture that some of the movements in plants 
may be attended by a like contraction. It is much to be desired 
that some one with the necessary leisure and appliances should 
institute experiments on this singular little Lycopod. 
It seems clear at any rate that light has as much to do with 
the movements of some of the lower organisms as it has 
with the direction of branches of leaves and flowers. Here 
also we may refer to the extraordinary rhythmical tremors 
observed by M. Lecoq, of Clermont, in the leaves of Colocasia 
esculenta. These are stated to occur at intervals, the plant in 
the meantime being perfectly at rest; so violent are the vibrations, 
according to M. Lecoq, that on one occasion the very pot in 
which the plant was growing shook so violently that it could with 
difficulty be steadied ! This statement has been confirmed by 
another French naturalist. It may be remarked that the emis- 
sion of water from a pore near the apex of the leaf has been 
occasionally observed ; hence it has been suggested that in the 
case of M. Lecoq’s plants, the tremors may have been occasioned 
by the efforts of the plant to rid itself of the water. Certain it 
is that in many cases no such aperture is visible in the plant in 
question, and that the emission of water is not by any means a 
common phenomenon. We must wait for fuller details before 
it can be decided whether the perforate or imperforate condition 
of the leaves has anything to do with the actions in ques- 
tion. Prof. Lecoq is too well known as an acute observer to 
allow of his statements being questioned on light grounds. 
Adverting now to sensitive plants,” specially so called, ap- 
parently from the fact that the movements they exert may be 
set in action by mechanical agency, as by a touch with the 
finger or other object, by a breath of wind, &c., it may be 
remarked that the numbers possessing this property are much 
larger than is usually supposed. 
Leguminosce and Oxalidacece afford the greatest number of 
such plants, and they have this in common, that the mobile 
leaves are ‘^compound,” consist not of one piece, but of several 
secondary leaflets, jointed to a common stalk, the ‘‘joint” being 
evidently the part most concerned in the movements that take 
place. Mimosa pudica and M. sensitiva are the two “sensitive 
plants” most commonly grown in this country. In either, a slight 
touch upon the extremity of one leaflet causes the depression of 
that leaflet, then of its neighbour, and so on in succession till. 
