PLATE XIII. 
Fig. 7. 
One lobe of an anther 1 in cross section showing a primary 
sporogenous cell. 
Fig. 8. 
Fig. 9. 
Fig. 10. 
Fig. 11. 
Fig. 12. 
Fig. 13. 
Spore mother cells in anther lobe. 
Microspore mother cell previous to synapsis. 
Mother cell in synapsis. Wall thickening at the corners. 
Metaphase. 
Completion of the heterotypic division. 
Metaphase of homotypic division. One spindle in cross sec- 
tion; the other in longitudinal section. 
Fig. 14. 
Completion of homotypic division. Mother cell wall con- 
stricting along the lines midway between the nuclei. 
Fig. 15. 
Three nuclei of the tetrad. The fourth lies below the plane 
of focus. 
Fig. 16. 
Thickening of the “special wall” completed. Microspore walls 
beginning to thicken. 
Fig. 17. 
Fig. 18. 
Fig. 19. 
Fig. 20. 
Spores at time of disintegration of the mother cell wall. 
Mature microspore. 
Cross section of microspore showing the grooves in the wall. 
Pollen grain with tube and generative nucleus. 
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