1917] DUNN—DUMONTIA 461 



to its longitudinal axis, and is parallel to the surface of the thallus. 

 The chromatophores in the tetraspores are hollow, oval bodies 

 with perforated walls. The mature tetraspores do not round off 

 while imbedded in the thallus. They escape either by the dis- 

 integration of the cells surrounding them or by a pore formed in 

 the wall of the thallus. 



The spermatia form a continuous layer over nearly the entire 

 surface of the thallus. The spermatium mother cells terminate 

 the branches forming the cortex and subcortex. The chromato- 

 phore which is present in the young spermatium mother cell 

 partially or completely disappears as this cell matures. The pro- 

 toplasm which was in the chromatophore is used in forming the 

 granular cytoplasm of the mature cell. The youngest spermatium 

 mother cells observed were binucleate. The first spermatium is 

 cut off diagonally. The mother cell may again become binucleate 

 and cut off a second spermatium in a similar manner on the side 

 opposite to that on which the first was formed. The second 

 spermatium may be formed while the first one is still attached to 

 the mother cell. No chromatophore is present in the spermatium. 

 The nucleus is situated at the distal end of the spermatium in a 

 dense mass of cytoplasm. The proximal end is vacuolated. The 

 spermatium is cut off from the mother cell as a cell and not as a 

 naked protoplast. 



The distribution of carpogonial branches in the young female 

 plants is general, as in the case of the tetrasporangia in the tetra- 

 sporic plants. The carpogonial branch develops by apical growth 

 and arises as a lateral outgrowth of a large subcortical cell. A 

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

 (6 cells always lie in a row). The basal cell ("cell 1") sometimes 

 divides to form a lateral cell. The carpogonium in a mature 

 branch is always close to or in contact with "cell 2" or "cell 3." 

 The sporogenous filaments always arise from one of these two cells. 

 Only a few trichogynes were found projecting beyond the surface 

 of the thallus. Spermatia were found fused to 4 trichogynes. 



Each carpogonial branch which has been fertilized produces 

 2 or 3 sporogenous filaments, all of which arise from one cell. It 

 is thought that the nuclei in these filaments are descended from 



