i 9 1 7] DUNN— DUMONTIA 449 



cell is apparently of no significance, because the nucleus from the 

 sporogenous filament enters here just as it does in the uninucleate 

 auxiliary cell (fig. 57). Oltmanns reports that the sporogenous 

 filaments in Dudresnaya purpurifera and D. coccinea branch freely. 

 These filaments in Dumontia apparently branch only occasionally 

 (figs. 42, 43). In both species of Dudresnaya no septa are formed 

 in the filaments except when they fuse with the auxiliary cells. 

 When the septa do occur, they are formed in the filament on both 

 sides of its point of fusion with the auxiliary cell. The tip of the 

 filament may then grow on to fuse with 2 or 3 more auxiliary cells. 

 In Dumontia only one case was observed in which a filament has 

 actually fused with an auxiliary cell and does not also terminate 

 in the cell (fig. 43). No septa were seen in this filament. A few 

 filaments growing over auxiliary cells were observed, but in these 

 cases there was no indication of any fusion (figs. 44, 53). The 

 sporogenous filament in fig. 43 branches just before it terminates 

 in the auxiliary cell. 



CYSTOCARPS 



Carpospore development is initiated by the formation of 3 

 or 4 gonimoblast filaments, of about 3 cells each, which arise suc- 

 cessively from the lateral protrusion of the auxiliary cell. These 

 filaments branch once, often twice, and every cell forms a spore 

 (figs. 56, 59). The cells at first are uninucleate (figs. 56, 58, 59, 63). 

 At a little later stage they become binucleate and divide (fig. 62). 

 No sterile cells are present at the base of the gonimoblast filaments. 

 The carpospores when first formed are rounded or subangular and 

 about 11 ju in diameter. They are well filled with a spongy cyto- 

 plasm which contains many small vacuoles (fig. 63). No chroma- 

 tophores are visible, but often a number of small dark staining 

 granules are present. When the nucleus is in the resting state, all 

 the chromatin is in the nucleolus. In the young cystocarp there 

 are generally present 3 or 4 cells of the auxiliary cell branch (figs. 56, 

 58, 63), and sometimes as many as 5 (fig. 62). A portion of the 

 auxiliary cell branch is often present even in the mature cystocarp 

 (fig. 60). The wall of the cystocarp is formed by branches which 

 grow out from these subcortical cells that have been displaced 

 inward by the enlargement of the group of carpospores (fig. 63). 



