BIOLOGY OF HIGHER SEED PLANTS 39 



If not, find a cell in which this is the case. 

 Note the relation of the cell plate to the 

 spindle. 



(d) The cell cytoplasm. What is its relation to this 



second spindle ? Is the cytoplasm reforming 

 hetween the daughter nuclei ? 



(e) Draw a stage in cell division, indicating the 



structure of the daughter nuclei, the spindle, 

 and the cell plate. Draw the cytoplasm in 

 one half of the cell. Make one drawing of 

 the spindle and cell plate in which the cell 

 plate extends completely across the cell. 



SUPPLEMENTARY STUDIES IN MITOSIS 



1. Prophase. Search for nuclei which illustrate the condensa- 

 tion of chromatin from the resting stage into the chromo- 

 some condition. See the text on the following changes 

 in the chromatin during prophase. 



a. Irregular dense masses of chromatin. Observe and draw 



one or more nuclei in which the chromatin has con- 

 densed into irregular dense masses. Is there any definite 

 arrangement of these chromatin masses ? 



b. Regular spiral arrangement. Observe nuclei in which the 



chromatin appears in a regular spiral thread in the 

 nucleus. This is usually termed the spireme stage. 

 Does the chromatin appear to form a continuous ribbon 

 or is it segmented into rods or chromosomes ? What 

 changes transform this ribbonlike arrangement of chro- 

 matin into definite chromosomes ? Is there any evidence 

 of a spindle's being formed at the poles of the nucleus 

 you are examining ? 



c. Draw the nucleus with the chromatin. Indicate the begin- 



ning spindle and surrounding cytoplasm, if the spindle 

 is forming. 



