I 



1917] DUNN—DUMONTIA 447 



after it has discharged its nucleus- The carpogonium is much 

 smaller than the cell which produces the sporogenous filaments, 



m 



the fusion of the two cells. 



The sporogenous filaments in Dumontia, according to Schmitz 

 (13), grow out from the carpogonium and do not fuse with any cell 

 in the carpogonial branch. This statement obviously is not correct. 

 One cell of the carpogonial branch in Dumontia may produce three 

 sporogenous filaments (fig. 42). A mass of fairly dense cytoplasm 

 which always contains a nucleus and sometimes a chromatophore 

 is present at the tip of each filament (fig. 42). The remainder of 

 the filament appears to be entirely empty. The sporogenous 

 filaments in Dudresnaya purpurifera (Oltmanns 9) arise from the 

 carpogonium and do not fuse with any cell in the carpogonial 

 branch. A carpogonial branch in D. purpurifera and D. coccinea 



- 



produces 2 or 3 sporogenous filaments. Each of these filaments in 

 D. coccinea fuses with a cell of the carpogonial branch before grow- 

 ing out into the tissue of the thallus. All the cytoplasm in the 

 3 sporogenous filaments in D. purpurifera is derived from the carpo- 

 gonium, in D. coccinea from the carpogonium and 3 other cells of 

 the carpogonial branch, and in Dumontia from either the second 

 or third cell of the carpogonial branch. 



AUXILIARY CELL BRANCHES 



The auxiliary cell branches of Dumontia have the same origin 

 and the same distribution as the carpogonial branches, but they 

 are not so numerous as the latter. The ratio of carpogonial to 

 auxiliary cell branches, considering the average number of branches 

 initiated on a plant, is . approximately 7 to i. The carpogonial 

 branches are very numerous in certain regions, as at the base of 

 the mature cystocarpic plant. The auxiliary cell branches are 

 found to predominate over the carpogonial branches at slightly 

 higher level on this same plant. 



The mature auxiliary cell branches vary in length from 4 to 6 

 cells (figs. 44, 45). The basal cell, just as in the carpogonial branch, 



may cut off a supernumerary cell (figs. 43, 45> 4°)- Tne size oi 

 the cells and the mode of development of the auxiliary cell branch 



