1917] DUNN—DUMONTIA 455 



exactly similar to that in Nemalion (Wolfe 19). Nearly all the 

 chromatin in the resting nucleus of Dumontia is in the nucleolus, 

 and, as in Nemalion and Griffithsia (Lewis 6), this chromatin passes 

 out along the nbrillae to the periphery of the nucleus. The number 

 of granules present in Griffithsia and Nemalion seems to be about 

 twice the number of chromosomes formed. This may be the case 

 in Dumontia also, although in this form the number of granules 

 seems proportionately larger. There is no indication of any chro- 

 matin being expelled from the nucleus of Dumontia as it is in 

 Griffithsia. 



Discussion and results 



The auxiliary cell branch and carpogonial branch of Dumontia 

 filiformis resemble each other very closely in origin, mode of develop- 

 ment, and structure. This similarity is so great that in some cases 

 it is almost impossible to determine the character of a branch. 

 The number, arrangement, and contents of the cells may be the 

 same in these two kinds of branches. The trichogyne persists for 

 only a short time after it has functioned. Hence the absence of 

 this structure is not a safe criterion for distinguishing the auxiliary 

 cell branches. The carpogonial and auxiliary cell branches differ 

 greatly from the vegetative branches in the size and contents of 

 their cells. It seems quite possible that the auxiliary cell branches 

 in Dumontia once bore trichogynes and functioned as carpogonial 

 branches. This similarity in structure of the auxiliary cell and 

 carpogonial branches is almost as marked in Dumontia as in Du- 

 dresnaya coccinea. The auxiliary cell branch of D. coccinea consists 

 of 12 cells and the carpogonial branch of 7 cells (Oltmanns 9); 

 otherwise the two kinds of branches appear similar in origin and 

 structure and differ greatly from the vegetative branches. 



It has been stated that the auxiliary cell branches and carpo- 

 gonial branches of Dumontia are probably homologous structures. 

 If this is true, the sporogenous filaments were probably developed 

 at the time when certain carpogonial branches ceased to be capable 

 of fertilization. The male plants in this species of Dumontia are 

 present for only 2 or 3 weeks during each spring. The ratio of 

 the number of female to male plants at the time when the latter 

 are supposed to be at the height of their development is 3 to 1. 



