1898 ] CELL DIVISION IN PINE SEEDLINGS 243 
part of the achromatin (figs. g-rz), and segments just before 
the spindle elongates to definite points. The nuclei in which I 
was able to count the segments contained sixteen chromosomes 
(fig. 14). They are somewhat difficult to count as they are 
usually massed together. Strasburger® counted twelve chromo- 
somes in the pollen grain of Pinus silvestris. Dixon? found 
eight, twelve, and twenty-four chromosomes in the gametophyte 
of Pinus silvestris, with eight as the prevailing number. The 
nuclei in the primary meristem of the growing point of Pinus 
Laricio and Picea orientalis were found by the same author to con- 
tain sixteen chromosomes. 
The chromosomes are at first scattered throughout the 
nucleus, but are gradually drawn toward the center to form the 
mother star (fig. 75). They seem to be arranged somewhat 
irregularly during this and the metakinesis stages (figs. 15, 20, 
22). The longitudinal splitting of the chromosomes takes place 
about the time of the mother star’stage. The daughter chromo- 
somes then move toward the poles where they arrange them- 
selves into the two daughter stars and form the network of the 
resting nuclei (figs. 28, 29). The spindle is usually quite 
pointed during metakinesis (fig. 22).. Sometimes, however, when 
the cell is short, the spindle does not become pointed but 
remains dome-shaped (fig. 78), giving an appearance similar to 
that which would be produced by the spindle fibers passing 
through the cell wall. The centrosomes, however, show that the 
poles lie very close to the cell wall. /ig. 77 shows one end of 
such a spindle with a double centrosome. In fig. 24 the sides of 
the spindle are concave. This shape was probably produced by 
the protoplasm contracting near the lower end of the spindle. 
Radiations are more prominent during the anaphase than dur- 
ing either the earlier or later stages (figs. 19, 23; 25). 
The centrosomes in Pinus appear as small but definite and 
readily stained bodies lying at the poles. Sometimes a hyaline 
area is visible around them in which the spindle threads termi- 
® Ueber das Verhalten d. Pollens. Hist. Beitr. 4: —. 1892. 
° Ann. Bot. 8: 21-34. 1894. 
