454 BOTANICAL GAZETTE [june 



fig. 53, is evidently just dividing. All of the chromatin in the 

 nucleus of this cell is in 14 granules of approximately the same size. 

 Nuclei which are probably preparing for division often contain 7 

 similar chromatin bodies (cell 3, rig. 51; cell 4, fig. 55; fig. 81). 

 It is thought that the chromatin bodies in these nuclei may be 

 chromosomes. Nuclei in the earlier stages of division contain 

 16-24 granules (cells 1 and 3, rig. 52; figs. 79, 80). These granules 

 must become grouped together to form the chromosomes. Thus 

 possibly the haploid number of chromosomes in Dumontia is 7. 

 However, it is evident that not enough data have been accumulated 

 to determine with any degree of certainty the number of chromo- 

 somes. These larger chromatin bodies in some of the nuclei are 

 vacuolated (cell 3 , tig. 5 1) . All the chromatin in the resting nucleus 

 is in the nucleolus, hence the chromosomes must fuse together after 

 division. It is quite possible that all the chromosomes do not fuse 

 at one time. Thus in fig. 82 each of the 2 large chromatin bodies 

 in the nucleus which contains 5 may have been formed by 2 chromo- 

 somes fusing together. If the fusing continued, the nucleus would 

 appear quite similar to that in the adjoining cell. When the nucleus 

 is being organized after division, the nucleolus appears granular, 

 and a few small chromatin bodies may, for a time, remain outside 

 of it (fig. 62). In the nucleus of the mature carpospore the linin 

 net is well developed, and all the chromatin is in the nucleolus, 

 which always contains at least one vacuole (fig. 66). Our knowl- 

 edge of the details of mitosis in this species of Dumontia is as yet 

 very fragmentary. The stage represented in cell 3, fig. 52, is 

 similar to the prophase of Delesseria as described by Svedelius 

 (15). This cannot be the prophase in Dumontia because the 

 granules present at this stage collect together to form larger units, 

 probably chromosomes. 



In Polysiphonia (Yamanouchi 20) and Delesseria (Svedelius 

 15) the chromatin from which the chromosomes are formed is 

 never contained in the nucleolus. It is distributed in fine granules 

 along the linin threads. The granules are in groups or short rows, 

 each one of which represents a prochromosome. A chromosome 

 is then formed by the fusion of several granules. Mitosis in 

 Dumontia up to the time of chromosome formation seems to be 



