20 BOTANICAL GAZETTE [july 



mined. The paucity of investigations on the somatic mitoses in 

 plants leaves open the possibility that some of the phenomena of the, 

 reduction mitosis to which a special significance has been attached 

 may find their counterpart in ordinary somatic mitoses. It is believed 

 that further study will settle the interpretation of these appearances- 

 Measurements have shown that the size of the cells, nuclei, 

 and chromosomes in the anther wall is on the average approxi- 

 mately the same as in the petals, though there is considerable varia- 

 tion in the size of the cells of the latter. It is interesting to note that 

 w^hile the chromosomes in the somatic tissues are loops in the meta- 

 phase and early anaphases, in the pollen mother cells the chromo- 

 somes are usually spherical or pear-shaped in these stages of both the 

 reduction mitoses. This difference is- very striking. In the telophase* 

 of the homotypic, however, the characteristic shape is apparently the 

 same as in the corresponding stage of somatic mitoses, that is, two- 

 lobed. Measurements indicate that the somatic chromosomes are at 

 this stage considerably smaller than the homotypic chromosomes, 

 though there appears to be much variation in the size of the former. 



SUMMARY 



1. In my previous paper the sporophyte number of chromosomes 

 in O. lata was found to be fourteen, and in the Lamarckiana hybrid 

 obtained by crossing O. lata with O. Lamarckiana pollen, at least 

 twenty. The number of chromosomes is now found to be twenty or 

 twenty-one constantly in all the plants of the Lamarckiana hybrid 

 examined, while the number in the pure O. Lamarckiana,'^^ as well as in 

 O. lata^ is fourteen, the reduced number being seven. These results 

 are obtained from a large number of counts in various stages of the 

 reduction mitoses and also in the somatic divisions (floral tissues). 

 Thus the pure O. Lamarckiana and the Lamarckiana hybrid, which 

 are identical in external appearance, differ widely in the number of 

 their chromosomes. 



2. The origin of the bodies called heterochromosomes, which are 

 present in the reduction divisions in all the forms studied, is a matter of 



25 J. M. Geerts, in a short paper just received (Ueber die Zahl der Chromo- 

 somen von Oenothera Lamarckiana, Ber, Deutsch. Bot. Gesells. 25:191-5. pL 6. 

 1907^, also finds that the sporophyte number of chromosomes in the pure O. Lamarck- 

 iana is 14 and the gametophyte number ■/• 



