180 BOTANICAL GAZETTE [MARCH 
derived. Cells such as those shown in fig. 53, situated within 
the borders of the meristem region, whose shapes vary but 
slightly from the typical embryonic cell, have noticeable differ- 
entiations ushered in even before the membranes of the daughter 
nuclei are formed. In the cell shown in fig. 53 of the anaphase 
the daughter chromosomes can be seen pushing into the cyto- 
plasm as the spireme coils are being formed. This is the first 
visible elongation of the nucleus. 
It cannot be said, then, that the peculiar shape of the nucleus 
is an adaptation to the shape of the cell, as in this case no appre- 
ciable elongation of the cell body has yet appeared. The causes 
which lead to this differentiation must be inherent in the chro- 
matic substance where it is initiated. 
In figs. 52, 54 of the telophase the elongation of the daughter 
spiremes can be seen. These early elongations give to the 
daughter nuclei an amoeboid shape. Such appearances in the 
various stages furnish evidence that the chromatic substance is 
here of a fluid nature, with the power of independent motion, 
and not a substance passively drawn by contractile threads of 
kinoplasm. 
When the cells by successive division have reached their 
maximum of elongation, further changes can be seen to have 
taken place within the nucleus. The chromatin, instead of being 
separable into groups of fours, as in the earlier stages of elongat- 
ing cells and as described in this investigation for the meristem 
cells, becomes vacuolar, the chromatin irregularly massed, while 
the nucleoli, which up to this time have been undergoing a con- 
siderable increase in size, suffer fragmentation. 
The observations then drawn from the anatomical differentia- 
tion in both types of cells found in the plerome point to the 
conclusion that the chromatic substance must play the chief role 
in the transformation of an embryonic cell into a tissue element. 
The same general statements as to the part played by the 
chromatin in the transition of the meristem cells into periblem 
and dermatogen can be made. The shape assumed by the chro- 
matic figure in karyokinesis determines the shape of the daughter 
cells. As the chromatic substance may elongate in the meristem 
