Aug., 1922.] 



SINOTOO— OENOTHERA LAMABCKIANA. 



93 



were cut 5—20 fi in thickness for the study of mitotic figures, and 

 60 — 120 {J. for counting the pollen grains. For the germination test 

 of the seeds the method described by Davis(2) was adopted. 



Abnormal behaviors of chromosomes in the meiotic divisions 



According to former investigators of the Oenothera cytology, the 

 meiotic chromosomes, especially in the heterotypic division, are loosely 

 paired and the regular nuclear plates are rarely found. It seems to 

 the writer, however, that the case is a little different as far as his 

 material is concerned. As the result of the calculation carried on in 

 more than one thousand pollen mother-cells in five preparations, the 

 number of the pollen mother-cells with the homologous chromosomes 

 paired in the heterotypic metaphase, or with those showing the 

 regular nuclear plates amounted to about 50 per cent. Nevertheless 

 the irregular phenomena in the chromosomal behaviors on the spindles 

 were also observed. Besides the various cases of the 

 abnormal behaviors of certain chromosomes in the 

 pollen mother-cells of the lata-semilata series of mutants, 

 classified by Gates and Miss Thomas(6), a few other 

 cases were found in the pollen mother-cells as well as 

 in the embryosac mother-cells of the present material. 

 Partly following the classification of Gates(5), the 

 following ten cases may be given : i. fourteen chromo- 

 somes in heterotypic or homotypic divisions make the 

 (8 + 6) or (9+.5) distributions (Text-figs. 1 ) 2.a,b,c and 

 3. a) — eleven cases of the (8 + 6) distribution in hetero- 

 typic mitosis (Figs. 13, 17, 19, 30, 33) and seven cases 

 in homotypic (Text-figs. 2.6, c and 3. a), one case of 

 the (9 + 5) distribution in heterotypic mitosis (Text-fig. 

 1) ; ii. certain chromosomes seem to divide into two 

 on the heterotypic spindles (Figs. 11, 12, 24, 29, 30) ; 

 iii. some of the heterotypic or homotypic chromosomes 

 undergo fragmentation or degeneration (Text-figs. 2. a, 



Text-fig. 1. 

 An embryosac 

 mother-cell in 

 heterotypic 

 metaphase. 

 X950. 



3. a and Figs. 29, 30); iv. some anaphasic chromosomes 

 leave a trail of chromatin behind ; v. certain chromo- 

 somes of both divisions are left outside the two 



1) All other figures except the four text-figures in this paper are to be referred 

 to those in the before mentioned writer's paper in Japanese. 



