392 
CLIFFORD H. FARR 
Nicotiana (6), it was shown that orange-staining granules apparently 
arrange themselves in rows to form the fibers of the new spindles after 
the second nuclear division. It is scarcely conceivable that so many 
fibers could be present in the cytoplasm as such during mitosis and 
not be detected. A greater probability seems to be that the material 
of the old spindle may have become dissipated throughout the cyto- 
plasm and have formed the orange areas, later to be used again in 
forming the new fibers. 
The furrows after the second division begin as sharp cutting edges 
formed by the infolding of the plasma membrane at its juncture with 
the equator of each spindle respectively (fig. 24). It will be observed 
that the secondary heterotypic spindle meets the plasma membrane 
at the summit of the heterotypic furrow, so that a new furrow is 
superimposed on the arrested one. The new one is always narrower 
than the older (figs. 14 and 24), so that their place of union remains 
marked throughout the process of furrowing. This superposition of 
the secondary heterotypic furrow on the primary one, as well as the 
usual elongation of the cell parallel to the heterotypic spindle, results 
in the equator of the latter being very narrow as compared with that 
traversed by the two homoeotypic spindles (figs. 13 and 25). In 
fact, the width of the secondary heterotypic spindle is frequently less 
than that of either homoeotypic spindle alone. Consequently, if all 
the furrows deepened with the same rapidity the cell would be divided 
into two parts first and then each of these would undergo bipartition 
by the homoeotypic furrows. This seems to be only rarely the case, 
and it is probable that the heterotypic furrow always develops some- 
what more slowly than the homoeotypic furrows (fig. 15). In most 
instances there is apparently perfect quadripartition (fig. 17) due to 
the retardation of the speed of development of the secondary hetero- 
typic furrow; but in a few cases (fig. 18) it is probable that the latter is 
completed slightly before the homoeotypic furrows have entirely 
closed their isthmuses. 
Cases of normal cell plate formation are quite abundant in the cells 
composing the anther walls of these same stamens (fig. 19). It may 
thus be concluded that all cells of Magnolia except the pollen mother 
cells divide in this way. The plate appears in the center of the spindle 
first, as described by Strasburger (15) and Timberlake (16), and then 
develops centrifugally in the equator accompanied by the formation 
of new fibers and the widening of the spindle. This process continues 
