236 BOTANICAL GAZETTE {APRIL 
between the fibers. In fig. 51 a clear space is noticed at one side of 
the dividing nuclear elements, whereas, in the more advanced stages 
shown in figs. 52-55, sap lies mainly between and separating the 
two active centers of division. In figs. 54 and 57, a region almost 
free from fibrous material separates the daughter halves and gives 
the appearance of a turgid, intranuclear, vacuolar cavity. It will be 
noted in these instances as well as in still later stages (jigs. 56, 58, 
60), that this nuclear fluid appears to exert pressure on the chromatic 
elements, as evidenced by the curved line where the massed chro- 
matic material borders on the vacuolar fluid. In fig. 56, which shows 
the next step in the division of the nucleus following jig. 57, the 
cytoplasm has constricted in two the mother-cavity, and in this 
figure as well as in the similar stages shown in jigs. 58, 60, it will be 
at once noticed that the solid constituents of the young daughter 
nuclei occupy a pseudosynaptic position, and that the greater part of 
the cavity of the daughter nucleus is occupied by a clear space. 
Whether an osmotic pressure of the intranuclear fluid causes this 
appearance, or whether it is due simply to the massing or contraction 
within the nuclear cavity of the chromatic elements about the polar 
centrosomes, can hardly be determined with certainty, but it is prob- 
° 
able that both forces are thus operative. 
Fig. 58 illustrates an interesting deviation from the more common 
median constriction of the elongated nucleus shown in jigs. 56, 59, 60. 
Here a double cytoplasmic constriction has taken place, resulting in 
two daughter nuclei and between them a vacuole, which is undoubt- 
edly filled with sap from the mother-nucleus. Probably in this 
instance the dividing nucleus became so greatly elongated that surface 
tension operated in such a way that the encroaching cytoplasm con- 
stricted it into three parts instead of two, as is usual. 
In fig. 59 is shown an early telophase condition in which the solid 
constituents of the nucleus are being redistributed throughout the 
daughter nuclei. Here the movement of chromatic material, as is 
characteristic for nuclei in this condition, is opposite to that seen in 
early stages of nuclear division. Whereas in the early phases this 
material moves toward and masses about the polar center, in the 
teleophases, it moves in the opposite direction, away from the center. 
In jig. 59 the center in each nucleus is still conspicuous, although a 
a 
