440 BOTANICAL GAZETTE [june 



the thallus and some which had actually reached the exterior 

 (fig. 1 8). Every spermatium seen outside the parent plant is 

 inclosed in a cell wall (fig. 41). No empty cell walls were seen 

 attached to the spermatium mother cell. Many spermatia were 

 seen lying close to the mother cells, but not attached to them (fig. 

 19). The spermatia in Dumontia are apparently cut off from the 

 mother cell in the same manner as they are in Polysiphonia (Yama- 

 xouchi 20) . The wall of the spermatium in both of these genera is 

 a portion of the wall of the spermatium mother cell, and no body is 

 formed which would be homologous to the spermatangium of 

 Delesseria (Svedelius 16). Svedelius (14) believes that the 

 spermatia in Martensia are set free in the same way as they are in 

 Polysiphonia. Lewis (6) states that in Griffithsia the spermatia 

 are cut off from the mother cells. This form can hardly be com- 

 pared with those previously mentioned, because in Griffithsia none 

 of the cells of the antheridial filament form cellulose walls, but all 

 are imbedded in the swollen wall of the mother cell of the branch. 

 The spermatia of Dumontia. as far as their contents are con- 

 cerned, are similar to most of those which have been described in 

 the other genera. The cytoplasm is much vacuolated at the 

 proximal end of the spermatium and is very dense at the distal 

 end. It is difficult to determine the structure of the nucleus, 

 because it is situated at the distal end of the spermatium, imbedded 

 in the dense, deep-staining cytoplasm. All the chromatin appears 

 to be in the nucleolus or in several chromatin granules collected 

 in the center of the nucleus (figs. 17, 19). 



CARPOGOXLAL BRANCHES 



Nearly all the carpogonial branches found in the mature female 

 plants were between the levels of 7 . 5 and 17.5 mm. from the hold- 

 fast. At levels higher up in the thallus, where mature cystocarps 

 occur, a few carpogonial branches are occasionally present. These 

 are not confined to one side of the thallus, but are scattered indis- 

 criminately among the cystocarps. Young cystocarpic plants 

 about 3 cm. in height were occasionally found even as late as July 5. 

 The few cystocarps which were present on these plants were at 

 the tips of the branches. Carpogonial branches were found in the 



