SPONTANEOUS MOVEMENTS IN PLANTS. 
371 
taneous motion possessed by detached portions of protoplasm 
endowed with the power of forming themselves into new indi- 
viduals. This phenomenon appears, however, to be but a 
form of the property possessed by all protoplasm of constant 
motion in some* form or other. The circulation of the proto- 
plasmic mucous fluid within the cells of plants is one of the 
most beautiful phenomena of vegetable life revealed by the 
microscope, and one of which the explanations at present 
offered appear quite inadequate. A favourite object for ex- 
hibiting this circulation or rotation is formed by the jointed 
hairs which cover the stamens of the Virginian Spider-wort 
( Tradescantia virginica). The movement is rendered visible 
by the presence in the otherwise colourless fluid of minute 
opaque granules of chlorophyll or other colouring matter ; and 
is observable with great ease in the semi-transparent tissue of 
certain water-plants, as Chara , or the Valisneria commonly 
grown in fresh-water aquariums. It consists of a slow move- 
ment of the protoplasmic fluid up one side of the cell, across 
the ends, and down the other side ; not perpendicularly, but in 
an oblique or spiral course. The subject has been carefully 
investigated by three French physiologists, MM. Prillieux, 
Roze, and Brongniart, who find that the rotation is directly 
influenced in a remarkable manner by the presence of light. 
M. Prillieux kept a moss in the dark for several days, when the 
cells presented the appearance of a green net-work, between the 
meshes of which was a clear transparent ground. All the grains 
of chlorophyll were applied to the walls which separate the cells 
from one another ; there were none on the upper or under walls 
which forrti. the surfaces of the leaf. Under the influence of 
light, the grains, together with the thin mucous plasma in 
which they are embedded, change their position from the lateral 
to the superficial walls, this change taking place, under favour- 
able circumstances, in about a quarter of an hour. On attaining 
their new position, the grains do not remain absolutely im- 
movable, but continually approach and recede from one 
another ; and if again darkened, they leave their new position, 
and return to the lateral walls. Artificial light produces the 
same effect as daylight. 
Analogous to the circulation of the protoplasm within the 
cell is that of the sap or nutritive fluid through the whole 
plant, passing through the permeable walls of the cells. This 
circulation of the sap, by which fluid is conveyed equally to all 
parts of the plant, apparently in opposition to the laws of 
gravity, is no doubt explicable to a certain extent by the ap- 
plication of known physical laws, of which the most important 
are capillary attraction, osmose, or the law by which a less 
dense fluid passes through a permeable diaphragm to mingle 
