division (p. 214 and Plate 6, fig. 88). A detailed study 
of one species, Hypericum Androsaemum L., revealed a 
more complete series of division figures which result in 
the formation of septa. 
In the normal formation of the fiber-tracheid from 
the cambium the cell undergoes elongation, forms bor- 
dered pits, and develops a thick secondary wall. The 
nucleus of the protoplast, shown in figure 1, is elongate- 
oval in shape. In general the long axis conforms to the 
long axis of the fiber-tracheid. Normally there are one or 
more nucleoli present. Following the normal maturation 
of the fiber-tracheid in this species, the protoplast re- 
mains active. This activity is expressed by the presence 
of mitotic division figures. Karyokinesis once initiated 
is followed by cytokinesis. In fixed material, spindle fi- 
bers are apparent in metaphase and in early anaphase (figs. 
2, 8and 7) and persist through the telophase (figs. 4 and 
8) until the daughter nuclei are distinct. The cell plate 
is well defined in the telophase just before the daughter 
nuclei emerge (figs. 4,5, 8 and 9). It appears to be formed 
by the equatorial expansion of the phragmoplasts which 
extend the cell plate and quickly intersect the walls of the 
cell. This is in accord with the type of cytokinesis found 
in all somatic tissue, the expression of which is dependent 
upon the dimension of the cell, the plane of division, and 
the location and size of the nucleus (5). The two daughter 
nuclei pass into a “‘resting’’ state migrating to the cen- 
tral position of the newly-formed compartments at ap- 
parently equal rates (fig. 6). The division is transverse 
to the axis of the cell instead of longitudinal as in the 
original cambial initial. 
The septum is formed in the region of the cell plate 
during cytokinesis. In mature stages it is always thin, 
in contrast to the heavy secondary wall as may be seen 
in figure 6. In staining reaction it resembles the primary 
[173 | 
