470 BOTANICAL GAZETTE [December 



segments medianly, that is, at the apex of the loop; 2.1- pairs of seg- 

 ments result; these separate to form \x chromosomes; a new 

 spindle is formed and 2X chromosomes pass to each pole. 



5. Fertilization may be regarded as having three phases: (1) sex 

 nuclei enter a common cytoplasm; (2) the two groups of chromo- 

 somes enter a common nuclear membrane; (3) the chromosomes 

 approximate in pairs. The first phase may be prolonged, as in 

 Uredineae; the second may be prolonged, as in some animals; or 

 the three phases may follow one another in rapid succession, as in 

 Abies. Attention is drawn to the similarity existing between the 

 phenomena connected with pairing in Abies and tetrad formation 

 in animals. It is suggested that they may be like processes occur- 

 ring at different stages of the life history. 



I wish to express my thanks for many suggestions and helpful 

 criticisms given by Professor J. M. Coulter and Professor C. J. 

 Chamberlain, under whose direction the investigation was 

 pursued. 



University of Chicago 



LITERATURE CITED 



1. Blackman, V. H., On fertilization, alternation of generations, and general 

 cytology of the Uredineae. Ann. Botany 18:323-326. 1904. 



2. — — , On the cytological features of fertilization and related phenomena 

 in Finns silvestris. Phil. Trans. Roy. Soc. B 190:395-426. 1898. 



3. Chamberlain, C. J., Oogenesis in Pinus Laricio. Bot. Gaz. 27:268-279. 

 1899. 



4. Coker, W. C, On the gametophyte and embryo of Taxodium. Bot. Gaz. 

 36:1-27. pis. 1-11. 1903. 



5. Ferguson, Margaret C, Contributions to the life history of Finns, with 

 special reference to sporogenesis, the development of the gametophyte, and 

 fertilization. Proc. Wash. Acad. Sci. 6:1-202. pis. 1-24. 1904. 



6. , The developement of the egg and fertilization in Pinus Strobus. 



Ann. Botany 15:435-479. 1901. 



7. Gregoire, V., Les cineses de maturation dans les deux regnes. La 

 Cellule 26:223-422. iqio. 



8. Harper, R. A., Sexual reproduction in the organization of the nucleus in 

 certain mildews. Pub. Carnegie Inst. Wash. no. 37. 1-92. pis. i-y. 1905. 



9. Hutchinson, A. H., The male gametophyte of Picea canadensis. Bot. 

 Gaz. 59:287-300. pis. 15-19. Jig. i. 1915. 



