THE DEVELOPMENT OF DUMONTIA 281 



E. TETRASPORES 



The cell contents. The cell contents and structure of the nuclei 

 in the tetraspores which have just been formed is quite similar to 

 those in the two-celled tetrasporangium (fig. 2, P, R). In the 

 mature tetraspore, the volume of cytoplasm and the size of the 

 chromatophores have increased. The protein granules have 

 entirely disappeared. The chromatophores lie in rows, some 

 at the periphery and some in strands of cytoplasm radiating 

 out from the nucleus (fig. 2, T). The chromatophores average 

 3.5At in length and 1.4^ in width. They are hollow, oval bodies; 

 and round perforations can be seen in the walls of some of them 

 (fig. 2, U). Thus they are quite similar to the chromatophores 

 occurring in the vegetative cells, but are very much smaller. 

 The mature tetraspores do not round off while embedded in the 

 thallus. 



The discharge of the tetraspores. The tetraspores escape 

 through a pore formed in the outer wall of the thallus. No 

 spores were observed in the actual process of escaping, but 

 many empty tetrasporangia were seen in the cross sections in 

 which mature tetraspores were also present. The ends of the 

 branches are often frayed out (fig. I, A), and it is evident that 

 the tetraspores might thus be torn free along with the vegetative 

 cells of the thallus. 



SXB'IMARY 



The mother cells of the tetrasporangia are subcortical cells. 

 The chromatophore of the mother cell segments into a number of 

 parts which persist through all stages of the tetrasporangium 

 and are present in the tetraspores. Mitosis in the tetrasporan- 

 gium is either not similar to that in the higher plants or is of 

 very short duration. 



THE PLANT WOELD, VOL. 19, NO. 9 



