iQoS] YAMANOUCHI—APOGAMY IX NEPHRODIUM 297 



ture seems to become influenced by the artificial conditions. The 

 growth becomes very slow, and the cells show a tendency to increase 

 greatly in size, while under normal conditions mitosis would occur 

 before such a size had been reached. Probably for this reason mitotic 

 figures are less frequently met during the growth of such prothallia. 

 As the cell increases in size, its nucleus grows large and the mitotic 

 figure is generally larger than in normal prothallia of this species. 



It was not difficult to find stages of mitosis in the vegetative cells, 

 and their comparatively large size facihtated the accurate counting 

 of chromosomes. The resting nucleus contains a dehcate reticular 

 structure consisting of a mixture of ragged clumps and slender threads 

 of chromatin. Nuclcoh with conspicuous peculiarities of form are 

 always present; sometimes there are two to several isolated round 

 nucleoli scattered irregularly within the nucleus, and sometimes part 

 of them are arranged into a group or groups. They are likely to be 

 mistaken for chromatin nucleoli, but after a close examination of 

 serial stages in the development of the chromosome it is clear that 

 they He entirely free from the chromatin network and do not seem 

 to contribute any material to the chromosomes by direct transforma- 

 tion. Cell contents beside the nucleus and cytoplasm are not so 

 abundant as in normal cases, the cell cavity consisting largely of 

 vacuoles. 



In prophase, the spirem is developed from the chromatin reticulum 



ih 



cal mitosis. 



ifig ^ 



{figs. 6, 7) show no peculiar delation from the typi- 

 he number of chromosomes is 64 (fig. S) or 66, W'lien 



two daughter nuclei are reconstructed, a cell plate is laid down 

 between them which finally divides the mother cell into two ceUs. 



In thi*; mofi^T-i'Ql fl-10 KiT^iioloofi^ i-r^nrlitinn \vn<s seldom obscrVcd, SO 



the 



mi 



tion of the nucleus of one cell to an adjacent one. 

 As stated before, mitosis in the ve^jetative cells 



agree 



to the axis of the spindle, which does not hold any regular relation 



iwn 



various directions. This is quite contran^ to the condition in normal 



