BOTANY: I. W. BAILEY 
285 
is not an artifact, i.e. due to the displacement of an ordinary spindle, is indi- 
cated by the fact that the whole mitotic figure is asymmetrically developed, 
in conformity with its diagonal position {D and E). 
Of course it is well known that the longitudinally dividing cells of the cam- 
bium form an exception to Sachs' law of 'rectangular intersection of succes- 
sive division-planes' and Hertwig's modification of Sachs' hypothesis, but it 
has been assumed by Giesenhagen and others that, in the cambium, the karyo- 
kinetic figures lie with their polar axes perpendicular and their equatorial 
planes parallel to the long axes of the cells. 
The formation of a cell-plate starting from one of these obhquely placed 
spindles is a very interesting phenomenon. The spindle becomes greatly 
extended laterally by the addition of peripheral fibers and gradually assumes the 
curved form shown in (E). As more peripheral fibers are successively added 
the remains of the central fibers disappear from about the cell-plate, leaving 
two separate aggregations of fibers which are connected by the first formed 
portion of the cell-plate (F) . These aggregations of kinoplasmic fibers, which 
may be called kino plasmas omes, have a very characteristic form and structure. 
They extend across the cell — at right angles to its longitudinal axis — from one 
radial wall to the other (C), and are located in the centre of the protoplast 
midway between its tangential surfaces (F). In sectional view (F), they have 
a somewhat wedge-shaped outline, bluntly convex in front and tapering to a 
point at the rear along the cell-plate. The kino plasmas omes move in opposite 
directions towards the ends of the cell {B and C). As they move forward, 
the cell-plate is extended until it eventually reaches the two ends of the cell, 
thus dividing the protoplast into two similar portions each of which contains 
one of the daughter nuclei. The latter remain close together near the centre 
of the cell during the process of cell-plate formation. The writer has been 
unable to demonstrate any visible connection between the daughter nuclei 
and the kinoplasmasomes or their constituent fibers. Except at the begin- 
ning of cell-plate formation the daughter nuclei are in a semi-'resting condition' 
and are provided with a clearly defined nuclear membrane and numerous 
nucleoli. Not infrequently the distance traversed by the kinoplasmasomes, 
in passing from the vicinity of the daughter nuclei to the ends of the 
protoplast, may be from one to several millimeters. 
This type of cell division, in which the process of cell-plate formation is 
so greatly extended — both as regards space and time — and so clearly disso- 
ciated from the usual phenomena of karyokinesis, promises, upon further 
analysis, to be of some significance in the discussion of the dynamics of 
cell division. 
^ Schacht and Russow claimed to have seen several nuclei in the cambial cells of Pinus. 
The writer is dealing with the normal longitudinal divisions of the cambial initials. 
