1898] KARYVOKINESIS IN THE ROOT TIPS OF ALLIUM CEPA 227 
it was thought best to take some such common object, which 
could be followed easily in the class room, and tested as to its 
accuracy. Accounts and figures of karyokinesis in plant cells 
are very scarce, and the so-called diagrammatic or schematic 
figures and descriptions given in most of the text-books are buta 
poor guide for the student and young investigator. For these 
reasons a rather complete account of the whole process has been 
given. 
The most typical resting nuclei occur some distance back 
of the tip beyond the actively dividing region. Here, in good 
stained material, the nuclei usually have one or two large 
nucleoli and a very distinct chromatin network, with large irreg- 
ular chromatin granules, which usually appear at the crossings 
of the meshes (fig. 7). In these cells there are large vacuoles, 
and it is rarely that the cytoplasmic contents or the centrospheres 
show to advantage. However, if one goes near the tip, in the 
actively dividing region, it is easy to find cells showing all the 
various cell organs usually present. The cells mostly divide in 
but one plane by transverse walls, and at the upper or lower side 
of the nucleus there is usually a depression in which two small 
bodies lie (fig. 2). The presence of this depression, and two 
characteristic bodies in it leave but little doubt as to their nature. 
They are to all intents and purposes centrospheres. Just at the 
time when the nucleus begins to divide it generally stains much 
deeper, and around it may be seen radiating streams of cyto- 
plasm (fig. 3). While the nucleus is in this condition the finer 
chromatin threads disappear. Just how this disappearance takes 
place it is not easy to tell. The finer meshes seem to be drawn 
into the coarser threads, or if this is not the case the whole 
thread shortens and thickens, thus becoming more evident, and 
also giving the appearance that there are fewer threads present. 
While this process is going on the centrospheres separate and 
take up their positions on opposite sides of the nucleus, being 
closely applied to the nuclear membrane (fig. 4). As the chro- 
matin thread continues to shorten and thicken the incept 3 of the 
3The word incept is used as the equivalent of the German An/age., 
