19 1 7l DUNN—DUMONTIA 441 



lower portions of the branches and in the main axis. The carpo- 

 gonial branches in Dumontia evidently are not formed in acropetal 

 succession. The carpogonial branches arise from the lateral 

 branches of the medullary hyphae. They arise either from the 

 basal cells of these subcortical branches or from cells intermediate 

 in position between the medullary hyphae and the surface of the 

 thallus. On the young plants every second or third large sub- 

 cortical cell or occasionally each successive cell produces a carpo- 

 gonial branch. Radial branches arise from the intervening cells. 

 In mature plants, where carpogonial branches occur only at the 

 base of the thallus, they develop from every fourth, fifth, or sixth 

 cell. Sometimes the same cell will produce two carpogonial 

 branches or one carpogonial branch and one radial branch (fig. 20) . 

 A mature carpogonial branch consists of 6 or 7 cells and a 

 trichogyne. If there are only 6 cells, they are all in a row. When 

 the carpogonial branch is composed of 7 cells, one cell may be formed 

 as a lateral outgrowth of the basal cell. For convenience and 

 clearness the cells of the carpogonial branch will be numbered. 

 The basal cell which is attached to the vegetative cell will be 

 numbered 1, the cell above it 2, etc. The first cell of the carpo- 

 gonial branches arises as a conical protrusion of the subcortical cell 

 (fig. 21). A portion of the peripheral chromatophore of the latter 

 is cut off in this protrusion. This first cell is uninucleate (fig. 22), 

 and divides by a wall parallel to its base (fig. 23). The chromato- 

 phore in each of these young cells of the carpogonial branches is 

 always peripheral, as it is in all the vegetative cells. The second 

 cell next divides transversely, thus forming a 3 -celled carpogonial 

 branch (fig. 24). No data were obtained concerning the details 

 of nuclear division in these earlier stages. This is due to the fact 

 that these stages persist for only a short time, and that the cells 

 are small and almost completely lined by the chrornatophores. 

 Considering the size and position of the cells in these young carpo- 

 gonial branches, it is evident that it must be the terminal cell which 

 divides each time. The cell wall separating the second and third 

 cells was barely visible in some carpogonial branches which had 

 just reached the 3-celled stage (fig. 24). These cells are separated 

 considerably at a slightly later stage (fig. 25). In the 4-celled stage 



