110 
IOWA ACADEMY OF SCIENCE 
EXPLANATION OF PLATES. 
Figures 1 to 12 refer to Trillium sessile, 13 to 23 refer to Arisaema tri- 
phyllum, and 24 to 46 refer to Zea Mays. 
Figures 1 and 2. Late prophase in pollen mother cells of Trillium. 
Figures 3, 4 and 5. Mother star stage. In 3 seen from pole of spindle. 
Figures 6 and 7. Metakinesis. 
Figure 8. Daughter star. 
Figure 9. Daughter skein, and incipient cell plate. 
Figure 10. Completion of division. 
Figures 11 and 12. Multinucleate cells from tapetum. 
