280 GRACE A. DUNN 



younger tetrasporangia. The protein granules are still present, 

 although they have decreased somewhat in size (fig. 2, 0). 

 The mode of division in the cases of tetraspore development 

 that have been recently worked out is tripartite. In such 

 divisions, the separation of the tetraspores is not completed 

 until they are discharged. The two cells formed at this first 

 division of the tetrasporangium of Dumontia are completely 

 separated. 



D. THE TWO-CELLED TETRASPORANGIUM 



Cell contents. The cytoplasmic contents of the cells have 

 increased. Chromatophores which stain very faintly are dis- 

 tributed in the cytoplasm lining of the cells and in the strands 

 radiating out from the nucleus. These chromatophores are 

 quite numerous; about 32 occur in a cell. They are consider- 

 ably flattened and appear as rows of small plates (fig. 2, P). 

 The protein granules are still present. They have decreased 

 greatly in size but not in number (fig. 2, P). It is quite possible 

 that the function of the protein granules may be similar to that 

 of the granules of Delesseria. While these protein granules in 

 Dumontia have been decreasing in size, there has been a marked 

 increase in the volume of cytoplasm and the number of chro- 

 matophores in the cells. The nucleolus generally contains a 

 vacuole (fig. 2, P). A small chromatin granule near the pe- 

 riphery of the nucleus is sometimes present in these nuclei as 

 well as in those of the tetraspores. 



Nuclear division. Only one stage in the second nuclear 

 division was observed. In this case the chromatin in each of 

 the two nuclei was in two spherical bodies (fig. 2, Q) . 



The two cells of the tetrasporangium may divide in parallel 

 planes or in planes which are perpendicular to each other (fig. 2, 

 R, S). The cells are completely separated in these two latter 

 divisions. 



