Centrifugal Force upon the Cell. 
361 
EXPLANATION OF FIGURES IN PLATE XVIII. 
Illustrating Professor Mottier’s paper on the Effect of Centrifugal Force 
upon the Cell. 
Fig. 1. Cladophora. A cell drawn eighteen hours after the action of a centrifugal 
force of 1930^- for one hour and a half. The displaced contents have begun to 
distribute themselves ; in the colourless part the plasmic lamellae are to be seen. 
Figs. 2 , 3. Cladophora. Both figures drawn two days after centrifugal action. 
In Fig. 2 cell-division had begun before the application of centrifugal force ; the 
cellulose-ring, appearing in optical section as two inward projections on either 
side, never developed further as a transverse wall. In Fig. 3 a division of the cell 
has just taken place. 
Figs. 4-6. Spirogyra. Centrifugal force, 1820^*, duration three quarters of an 
hour. Fig. 4 was drawn immediately after centrifugal action at 5 p. m. ; the two 
chlorophyll- bands, nucleus, and all cytoplasm capable of being displaced lie in 
a compact mass in the lower end of the cell. Relatively large starch-grains form 
a rosette about each pyrenoid. 
Fig. 5. A cell larger than in Fig. 4, drawn at 9 a.m. the following morning; 
the primordial utricle is thicker, due to a redistribution of cytoplasm over the inner 
cell-surface. The bands with the nucleus have made some progress toward re- 
distribution. Fig. 6 was drawn at a still later period. 
Figs. 7-9. Cells from the stamen-hairs of Tradescantia virginica. Centrifugal 
force about 1820^, duration one hour. 
Fig. 7. Karyokinetic figure at the close of the anaphase ; each set of daughter- 
chromosomes lies slightly inclined to the longitudinal axis of the cell. The 
beginning of the cell-plate is faintly visible ; the vacuole occupies the upper end 
of the cell. 
Pig. 8. Drawn twenty-two hours after centrifugal action ; cell-division took place 
while the nucleus lay in the displaced position, thus giving rise to two daughter- 
cells of greatly unequal size. The fact that the diameter of the nucleus of the 
smaller cell is almost as great as the length of the cell itself, seems to indicate that 
the cell was in process of division at the time of centrifugal action. 
Fig. 9 a-g (semi-diagrammatic) represents a part of the process of cell-division 
in a cell in which the dividing nucleus and surrounding cytoplasm were displaced 
transversely. Observation began immediately after centrifugal action ; a to f re- 
presents forty minutes,/ to g eight minutes. 
P igs. 10, 11. Cells of the leaf of Funaria. Centrifugal force 1700 to 1820^, 
duration one hour and a half. 
Fig. 10. A cell from basal half of leaf showing displaced contents. 
Fig. 11. Displacement in a cell which had been first plasmolyzed. 
Fig. 12. Nucleus from a cell of the plerome of a root-tip of Allium. From the 
displaced mass of nuclear thread, strands extend to various points in the nuclear 
membrane, especially to the sunken-in part opposite. The nucleolus was on the 
point of breaking through the nuclear membrane. 
Fig. 13. Part of a long cell from the plerome of a root of Zea Mays. The 
heavy nucleolus has drawn a part of the nuclear membrane out into a long neck. 
Starch grains and other inclusions lie in the lower end of the cell. 
