164 THE BOTANICAL MAGAZINE. [Vol. xxxv. Xo. 4i7. 



development of female gamates it seems to be probable that there is 

 a lethal factor or factors for the development of the embryo. And 

 the lethals of P. orientale might have been inherited and caused the 

 sterility of F plant ; i. e., not the lethals formed in the meiotic 

 division of F^ plant, but these inherited from the parent. 



Summary 



1. In the prophase of the meiotic division of the Papaver 

 hybrid, chromosomes forming gemini, unite end to end, not side b}' 

 side. 



2. There appear 11 bivalent chromosomes and 10 univalent 

 chromosomes in the first meiotic division. The bivalent chromosomes 

 form the equatorial plate first ; all the eleven chromosomes may pass 

 to the anaphase simultaneously, or seven of them first and remaining 

 four afterward ; the univalent chromosomes may follow the same 

 process after the halves of the bivalent chromosomes left the equator 

 for the opposite poles of spindle. They make the longitudinal split 

 at the equator and the halves move to the opposite poles. 



3. The univalent chromosomes, which remained outside the 

 spindle or did not get to the pole before the nuclear membrane 

 appears, are left in the cytoplasm. 



4. In the second divison of meiosis, the large chromosomes, 

 probably derived from the bivalent chromosomes from the equatorial 

 plate earlier than those from univalent chromosomes. 



As in first division, some chromosomes derived from the 

 univalent chromosomes are left in the cytoplasm. Some of them 

 remains as isolated chromosomes in the cytoplasm, but some, single 

 or two or more in groups are inclosed by themselves in separate 

 membranes and thus form miniature nuclei. 



5. As the result of the irregular behavior of the chromosomes, 

 occasionarily two daughter nuclei of the first division of meiosis, 

 connected by a bridge of isolated chromosomes, unite to form a 

 single nucleus. The union of two nuclei, beloning to two different 

 spindles of the second meiotic division, also takes place. The result 

 in the appearance much resemble an amitotic division. Such nuclei 

 form a kind of diploid pollen grains. 



6. The irregular behavior of chromosomes in the meiotic division, 

 the union of two nuclei, and dropping of certain chromosome cause 

 the abnormalities of pollen grains, not only in shape and size, but 

 also in the combinations of the heredity substances. 



