Pollen Mother-cells of Certain Plants . 53 
11. Each univalent portion of each bivalent diakinetic chromosome 
undergoes a longitudinal fission, forming apparent tetrads. 
12. The first or heterotypic division separates entire somatic 
chromosomes. 
13. The chromosomes remain distinct between the telophases of the 
first and the prophases of the second division (i. e. during interkinesis). 
14. The somatic chromosomes or prochromosomes appear in the pollen 
grain, arranged in a single univalent series. 
Madison, Wisconsin, 
July , 1908. 
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