24 



Veit Brecher Wittrock. 



above, the lateral and cone-shaped process does not appear immediately 

 under the top of the cell, but a space below it, which space is- in general 

 about as great as half the diameter of the mother cell. On this depends 

 the circumstance (mentioned page 4), so peculiarly characteristic in 

 Pithophoraceoe, of having the branches not at the very top of the sup- 

 porting cells, but a space below it. The small process formed in the 

 manner mentioned above is elevated more and more, and little by little 

 elongates, till it attains the form of a cylinder with a rounded top and 

 with its base, as it were, contracted (pi. 3, fig. 2 b). This process has 

 in general a position so as to form an angle of about 45 degrees with 

 that part of the mother cell which is situated above the process. When 

 this process has attained a length which exceeds the diameter of the 

 mother cell 2 — G times, a cell-wall is formed at its base, which sepa- 

 rates the process, as an individual cell, from its mother cell. This cell- 

 wall, which is formed exactly in the same manner as the transversal 

 cell-walls in the principal filament, has, now and then, a position -so as 

 to be almost rectangular to the process (pi. 4, fig. 2 and 6 w,-), but 

 generally it is placed obliquely against this axis, with an evident incli- 

 nation downwards (pi. 3, fig. 7 w; pi. 4, fig. 3, 4, 5, 11, 18 w>, and 

 others). Thus we find here an exception from the law indicated by 

 Hofmeister in Handb. d. Phys. Bot. Band I, Abth. 1. page 129, that 

 the parting wall formed at the bipartition of cells is rectangular to the 

 direction in which the strongest preceding increase of the cell has taken 

 place. x ) The daughter cell formed in the manner indicated above, and 

 placed at the side of its mother cell, and having as a rule a diameter 

 y — J / 4 shorter than that of its mother cell, now increases in length. 

 When it has grown about twice as long as the mother cell, it is divided, 

 in the usual manner, into two daughter cells, a lower one somewhat 

 shorter, and an upper one somewhat longer. It happens, more rarely 

 in sterile specimens, but oftener in fertile, that the branch cell, developed 

 from a cell of the principal filament, is not divided, in which case the 

 branch remains of course unicellular (pi. 1, fig. 8 b); but if a formation 

 of spores (in fertile specimens) in the branch cell takes place later, it 

 is thus made bicellular (pi. 2, fig. 4 6). Such branch cells do not, as a 

 rule, attain a length so considerable as that of those which are to form 

 new cells by bipartition. If, as the case most frequently is, the branches 



') »Die theilende Scbeidewand st'eht senkrecht auf der Richtung des starksten 

 vorausgegangenen Wachsthums der Zellew. Hofm. 1. c. 



