THE CAMBIUM AND ITS DERIVATIVE TISSUES 
plate comes in contact with the radial facets of the protoplast, the kinoplasm 
disappears from two sides of the frame-like figure, leaving two entirely sepa- 
rate aggregations of kinoplasmic fibrillae, which are parallel and which cross 
the cell from one radial wall to the other (fig. 58). These rod-like masses of 
kinoplasm (kinoplasmasomes) move in opposite directions, thereby extending 
the cell plate towards the ends of the cell. In radial, longitudinal sections 
of the cambium, the kinoplasmasomes are seen in section (figs. 20, 21). 
They are located midway between the tangential facets of the cell and 
usually are equidistant from the daughter nuclei or approximate center of 
the protoplast. This indicates, of course, that they move forward at equal 
rates. As shown in figure 22, they have a wedge-shaped outline, bluntly 
convex in front and tapering to a point at the rear along the cell plate. They 
are composed of fibrillae which resemble those that occur in the spindle. 
The threads or "lines of flow" do not extend across the cell from one tan- 
gential membrane to the other, but lie free in the cytoplasm. Nor are they 
connected with the daughter nuclei, which remain in their original position 
near the center of the protoplast. As new peripheral fibers are successively 
added in front, those at the rear disappear from about the recently formed 
portion of the cell plate (fig. 22). The latter is gradually extended in this 
singular fashion, often for a distance of several thousand microns, until it 
eventually reaches the ends of the protoplast; thus dividing the latter into 
halves, each of which contains one of the daughter nuclei. The nuclei 
become enclosed in a nuclear membrane and reform their nucleoli long before 
the kinoplasmasomes reach the ends of the cell. 
Similar phenomena occur in dicotyledons during longitudinal division 
of the fusiform initials (figs. 23, 24, 25), but, owing to the smaller size of the 
cells, the kinoplasmasomes and cell plates are smaller than in the Coniferae. 
The oblique partitions of fusiform initials, and the longitudinal and oblique 
divisions of their derivative cells, are also formed by the intervention of 
these extraordinary cell plates (figs. 27, 51, 54, 55). Furthermore, the 
writer has accumulated considerable evidence which indicates that the 
phenomena in question are not confined to the cambial layer, but that 
they occur in other somatic tissues of the higher plants, in elongated or 
much flattened cells whose planes of division have one long and one short 
dimension. 
Types of Cell Plate Formation in the Higher Plants 
It is of interest to inquire what relation this type of cell plate formation 
— which is so greatly extended, both as regards space and time, and so 
clearly dissociated, except in its initial stages, from the usual phenomena 
of karyokinesis — bears to those types which previously have been described 
by Treub (1878), Strasburger (1880), and Schiirhoff (1906). In Treub's 
first type, the nucleus is centrally located and the central spindle merely 
expands symmetrically until it touches the four walls of the isodiametric 
