SUNFLOWER APICAL BUD 85 



1. The thin cell-wall. 



2. The granular protoplasm with one or more vacuoles. 



3. The relatively large nucleus, which is sharply defined, and 

 contains fine fibrillse, which constitute a complicated coiled 

 filament or network of chromatin so fine as to give the whole a 

 granular or dotted appearance. 



4. One or more highly refractive nucleoli are contained in it. 

 Note the following changes in a cell undergoing division : 



1. The cell elongates, and the nucleus increases in size : the 

 fibrilla of chromatin becomes thickened, and the appearance of 

 the nucleus is more coarsely granular. 



2. The fibrilla of chromatin breaks up into a number of short 

 rods which straighten out and arrange themselves in two groups, 

 one on either side of the equatorial plane ; the rods of each group 

 are nearly parallel to one another, and converge slightly towards 

 the poles of the spindle-like figure, which form the whole nucleus 

 has now assumed. 



3. The two groups on either side of the equatorial plane 

 separate further, and the rods of each group become connected 

 into the fibrilla of the new nucleus. 



4. Fine granules appear in the equatorial plane and constitute 

 the cell-plate : they coalesce to form the new septum or cell- wall, 

 which by the widening out of the spindle at the equator, is attached 

 to the outer wall of the cell. The two new cells, each with its 

 nucleus, are thus separated by the new cell-wall which cuts the 

 old wall at right angles. 



Other preparations may be made by staining with solution of 

 methyl green in 1 per cent, acetic acid : in these the nuclei will 

 be more distinctly seen : also in those in which the spindle is 

 already formed, fine threads, the spindle threads will be seen 

 connecting the two new nuclei, and arranged relatively to one 

 another like the staves of a barrel. 



II. Cell-division as it takes place in the multiplication of cells 

 of an ordinary tissue may be observed in the young stems of the 

 Sunflower or Elder. On a warm day, cut young shoots of either 

 of these plants, in which the internodes are between one and two 

 inches in length : fix them at once in alcohol for twenty-four 

 hours or more, and from the tissue thus hardened cut longitudinal 



