On the PithophoeacejE. 27 



only oue sessile spore). Of P. keioensis nob. I have also found a spe- 

 cimen (see pi. 1, fig. 8) of wliich the top cell supports a branch. It is 

 possible, however, that this cell is not the real terminal cell of the plant, 

 but that it has been made terminal by the breaking- off in some way 

 of the uppermost part of the specimen. 



What has been said above on the formation of branches concerns 

 in the first place the normal branches, but also of the accessorial it 

 may, in its principal points, be true. Only the following deviations are 

 to be remarked regarding these. The place where they occur is, as 

 we know, different from that of the normal branches. In most cases 

 they are formed a small space above the base of their mother cell; and 

 when this is the case, they increase downwards instead of upwards (pi. 

 1, fig. 4, 18 ac; pi. 2, fig. 9 ac; pi. 4, fig. 7, 9 ac). ^) By this circum- 

 stance they get quite the same relative position to the basal part of 

 the mother cell, as the normal branches to the apical part. Only 

 very seldom accessorial branches are found of another nature. PL 5, 

 fig. 1 shows the lower part of a specimen, which possesses two acces- 

 sorial branches, ac and ac\ which proceed both, it is true, from the 

 lower part of their mother cells, but which are, nevertheless, placed 

 considerably farther from the base of the mother cell, than accessorial 

 branches usually are. What is most remarkable in these branches is, 

 however, that they have increased not in a downward direction, but 

 upwards, like the normal branches. Fig. 2 on the same plate also 

 shows two accessorial branches, ac, attached in a rather uncommon 

 place. — The accessorial branches generally remain imbranched; I have 

 only once found one which was ramified (pi. 5, fig. 1 ac). Most fre- 

 quently the}'' appear on the principal filament of the cauloïd and espe- 

 cially on its lowest cell. Now and then I have, however, found acces- 

 sorial branches proceeding also from branch cells. PI. 1, fig. 18 ac 

 shows an accessorial branch developed from a cell, belonging to a branch 

 of no less than the 2:d degree. 



Ramification, accompanied by bipartition (by which act common 

 branches, consisting of one or more cells, are formed), from terminal 

 cells is, as we have seen above, upon the whole very rare in Pithophoraceœ. 



') By comparison with the Cladophorece I have latei- come to the conviction, 

 that the basal accessorial tranches ought to be regarded as belonging to the root- 

 system of the plant, being the morphological equivalents of the rhizines, emitted from 

 the cauloïd cells of the Cladophorçœ. See par. 5, pag. 37. 



