606 Price. — Some Studies on the Structure of the Plant Cell 
As Gaidukov has already shown, particles of a larger order of magnitude 
frequently occur in the sap vacuole. In species of Spirogyra with a loose 
type of spiral these are usually very conspicuous, and to avoid their inter- 
ference with observation a close spiral type is useful. These ‘ sap particles ’ 
are found to be of very general distribution in plant cells (see § 5). 
In many cases it was possible to observe the nucleus, especially in 
starved or poorly nourished material of a large species, which was used for 
a long time for observation. As is well known, the nucleus is suspended in 
the cell-cavity by cytoplasmic threads ; these threads were clearly seen as 
slightly heterogeneous processes, stretching from the cytoplasmic layer of 
the cell to the cytoplasm surrounding the nucleus. They seem to be viscous 
in nature and show the larger microsomes clearly present. The microsomes 
here exhibit an oscillating movement and also a movement of translation, 
gradually passing one another in different directions, and giving an appear- 
ance of moving in a viscous medium. The appearance of the nucleus itself 
is described elsewhere ; it is differentiated in structure from the cytoplasmic 
mass which surrounds it. The microsomes move more especially on the 
outside of the cytoplasm which envelops the nucleus (see PI. XLII, Fig. 1). 
E lode a canadensis. 
At the edge, the leaf of this water-plant is only one cell thick, and these 
edge cells have proved quite useful for observation (Price, T 2 ). The young 
leaves are removed from the stem, carefully brushed to remove epiphytic 
growths and mounted in water. In these edge cells the wall is optically 
clear, and the chloroplasts are few and inconspicuous under dark-ground 
illumination (PI. XLI, Fig. 6). 
The protoplasm forms a general layer on the inside of the wall, sur- 
rounding a central vacuole, but threads and strands of protoplasm frequently 
cross the vacuole, the conformation of these constantly altering during the 
circulation of the protoplasm. The protoplasm is seen to be filled with 
large numbers of particles (submicrons), which appear as glittering points of 
light and are in a state of active Brownian movement. If circulation and 
streaming is not taking place, this generally soon begins, possibly under the 
slight warming which the leaf undergoes on the stage. The protoplasm flows 
on as a viscous liquid, carrying the particles with it, which retain their 
Brownian oscillations (Gaidukov, TO, p. 52). The particles in the stream 
seem to move with considerable rapidity. After a time the chloroplasts 
begin to be carried forward, as though the circulating stream took some 
time to acquire sufficient energy to do this. It is a significant fact that the 
chloroplasts never move as rapidly as the protoplasmic submicrons, so that 
their motion does not give an accurate measure of the rate of movement of 
the protoplasm (Pfeffer, ’ 06 , p. 289). No definite differentiation into endo- 
plasm and ectoplasm was made out. 
