272 THE BOTANICAL MAGAZINK , / [VoiT xxiy. i&-«8£ 



from one another (Text-fig. A. e, f), as is commonly the: case 

 with Monocotyledons. . / ; . 



In the polar view of the second diYiston, we find 12 chromo- 

 somes as is natural, but their behavior is very remarkable, in 

 presenting a paired arrangement (Text-fig. A. e, f, g) as we may 

 expect it in a diploid cell, but not in an ordinary homotype divi- 

 sion, or in a haploid cell. This peculiar behavior of chromosomes 

 in homotype division was first discovered by my friend Dr. M. 

 Tahara in Morris (14), and the present case with Oryza sativa is 

 the second example. In Oryza sativa not all of the 12 chromo- 

 somes form pairs, and some of them remain single, while there is 

 also a tendency among them to form a group of more than two or 

 three. Besides, it seems to me that the arrangement of chromo- 

 somes, though not in all cases, is somewhat similar in both sister 

 nuclei of the homotype division. This pairing of chromosomes 

 in the second division can not be looked upon as an artifact. 

 But its biological significance is left undecided for the present. 



The homotype division passes over otherwise in the ordinary 

 way and the four young pollen-grains are organized. 



The size of chromosomes observed in the maiotic phase is 

 by no means the same, but their individual difference in size is 

 not large enough to be recognized throughout the phases. 



Abnormal case of heterotype division. In the course 

 of this study I got a preparation, in which all the gemini were 

 somewhat smaller than the ordinary ones, and two or three of 

 them took a rod-shape (Fig. 16) which were quite small in the 

 polar view, when compared with the other gemini (Text-fig. A. 

 b). The material of this preparation was collected in a ' Shin- 

 riki ' rice- field, but the very plant to which this material belonged 

 was not specially noted. It is likely, however, that plants of 

 a different race grew mixed with ' Shinriki.' At the same time 

 there is no proof that this plant did not represent a mutant of 

 * Shinriki.' In fact I have observed a few plants, while collecting 

 the materials, which had, unlike usual ' Shinriki/ the dark violet 

 stigma. To know whether the latter plant has such chromo- 

 somes as above stated, I have specially collected the material 



