472 BOTANICAL GAZETTE [june 



4. Spindle fibers are the result of exosmosis of karyolymph into 

 the cytoplasm, these being formed after the same fashion as the 

 nuclear membrane. The membrane, if it persists, will be a part of 

 the fibers. 



5. The third contraction which accompanies fiber formation 

 consists of a balling up of the chromosomes previous to the complete 

 filling up of the cavity with fibers. 



6. Each chromosome is an osmotic system in itself and capable 

 of forming its own weft of fibers after the sap from the nuclear 

 cavity has been exhausted. 



7. The heterotypic division or the reduction of characters 

 results from a transverse separation of whole chromosomes. 



8. During early anaphase the halves of the chromosomes, 

 which originated in presynapsis, separate longitudinally and at 

 early telophase approximate end to end, forming the looping spirem 

 of the daughter nucleus, ix chromosomes in length. Division in 

 homotypic mitosis, therefore, results originally from a longitudinal 

 separation. 



9. The transverse separation of the 16 segments during early 

 metaphase of the homotypic mitosis is immediately followed by 

 their pairing. 



10. To all appearances a typical mitosis is begun, but is varied 

 and delayed for a time by a heterotypic mitosis as the result of the 

 various contractions, being finally completed in the homotypic 

 division. 



To Dr. J. M. Coulter and Dr. C. J. Chamberlain I wish to 

 express my appreciation for their most helpful suggestions and 

 criticisms during the progress of this work, and also to Dr. D. M. 

 Mother of Indiana University, under whom this work was 

 commenced. 



University of Chicago 



LITERATURE CITED 



1. Allen, C. E., Nuclear division in pollen mother cells of Lilium canadense. 

 Ann. Botany 29:189-258. pis. 6-g. 1905. 



2. Beer, R., Studies in spore development. II. On structure and division 

 of the nucleus in the Compositae. Ann. Botany 26:705-726. 1912. 



