On the Pithophorace.e. 



13 



of a parting wall, which is to divide the mother cell of the spore into 

 two daughter cells. The foundation of this parting wall is laid, in P. 

 kewensis nob., not at the point where the cask-shaped widening of the 

 cell commences, but a small space below this point (pi. 3, fig. 7 ba'). 

 The parting wall first appears as a narrow ring-formed ledge on the 

 inside of the original membrane of the cell. This ringformed ledge in- 

 creases successively inwards, so as to grow broader and broader (pi. 3, 

 fig. 7 ba\ and the hole in its centre consequently narrower and narrower; 

 till it is at last completely tilled up, and thus the parting wall quite com- 

 pleted. By this parting wall the mother cell is now divided into two 

 daughter cells, an upper one rich in chlorophyll and cask-shaped, the 

 spore, and a lower one, containing but little chlorophyll and cylindrical, 

 the sub sp oral cell. The spore which has been formed in this manner, 

 is completed by its membrane growing so much thicker, that it is at 

 last, in P. kewensis nob., twice or thrice as thick as it originally was 

 (pi. 3, fig. 9). A formation of clearly discernible layers in the mem- 

 brane does not take place here. The contents of the cell do indubit- 

 ably also undergo a change, for its colour, originally of a dark green 

 or almost blackisk green, changes into brown, probably by a part (or 

 all) of the granules of starch being transformed into a brownish oil. 



By this exposition it is shown, that in the formation of spores in 

 P. kewensis n ob. the following four stages may be distinguished: l:o The 

 cask-like widening of the upper part of the mother cell of the spore: 2:o 

 The passing of the chlorophyllaceous matter from the lower, cylindrical 

 part of the cell to its upper, cask-like part; 3:o The appearing, just- 

 below the cask-shaped widening, of a succedaneously formed parting 

 wall, and 4:o The ripening of the spore, situated above the parting wall, 

 by the thickening of the membrane and the transformation in part of 

 the contents of the cell. — The result of the whole process consequently 

 is, that the mother cell of the spore forms, by division into two, one cell 

 capable of germinating, the spore, in the formation of which the whole 

 chlorophyllaceous contents of the mother cell are consumed, and one 

 vegetative cell, the subsporal, which is not capable of further formation 

 of cells or increase of any kind, being devoid of protoplasm, and which 

 may consequently be regarded as being at least half dead. 



If you compare the other species of Pithophoracece with P. kewensis 

 nob. as to the process of the formation of spores, you will find, that 

 the formation of spores takes place, upon the whole, much in the same 

 manner, but withal that a couple of less essential deviations may occur. 



