I. W. BAILEY 529 



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form (Figs. 8 and 9). As more peripheral fibers are successively 

 added, the remains of the original central fibers disappear (Fig. 9) 

 from about the cell plate, leaving two separate aggregations of fibers 

 that are connected by the first formed portion of the cell plate (Fig. 

 10). These aggregations of kinoplasmic fibers, which I have called 

 kinoplasmasomes, have a very characteristic form and structure, both 

 in gymnosperms and angiosperms. When the initials are dividing 

 in the usual tangential longitudinal plane, the kinoplasmasomes 

 extend across the cell — at right angles to the longitudinal axis — from 

 one radial wall to the other (Fig. 12) and are located in the center of 

 the protoplast, midvv^ay between its tangential surfaces (Fig. 10). 

 In sectional view, they have a somewhat wedge-shaped outline, 

 bluntly convex in front and tapering to a point at the rear along the 

 cell plate (Fig. 10). They move in opposite directions towards the 

 ends of the cell (Figs. 11 and 12). 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 halves, each of which 

 contains one of the daughter nuclei {n). The latter remain close 

 together, near the center of the cell, during the process of cell plate 

 fonnation, and I have been unable to demonstrate any visible con- 

 nection between the daughter nuclei {n) and the kinoplasmasomes {k) 

 or their constituent fibers. 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 500 to 5,000 micra. 

 The two kinoplasmasomes usually, although not invariably, move 

 forward at equal rates, so that at any given stage they appear to be 

 equidistant from the starting point and daughter nuclei. Prelimi- 

 nary investigations indicate that the total time consumed in the proc- 

 ess of cell plate formation is considerable, in all probability a matter 

 of many hours rather than mxinutes. 



In the normal, tangential longitudinal divisions of the large initials, 

 the kinoplasmasomes, once they have curved into a position midway 

 between the tangential walls of the cell, move in a straight line 

 towards the ends of the protoplast; thus the division is a plane surface. 

 This is frequently not true, however, in the case of the semitransverse 

 divisions of the initials. The kinoplasmasomes meander more or less 

 in certain cases and curved or undulating surfaces are formed in 

 consequence (Text-fig. 3). 



