26 



Veit Breciier Wittrock. 



in half-fertile-half-sterile specimens, the formation of spores is begun 

 already before the ramification is completed (pi. 2, fig. 5, 7). It then 

 not seldom happens, especially in P. Cleveana nob., that the formation 

 of a branch being commenced in a cell, it is interrupted by the for- 

 mation of a spore in the same cell. A cell of this description then 

 seems to have, as it were, suddenly changed its plan, ceasing the for- 

 mation of the branch in order to form in its place a spore. Spores 

 formed during those circumstances are recognized by carrying on one 

 of their sides a greater or smaller process, often resembling the beak 

 of a bird (pi. 2, fig. 3, 14, 15 sr; pi. 3, fig. 8 sr). That the formation 

 of branches and spores may take place at the same time is also shown 

 by pi. 3, fig. 5. Here we find a branch process, formed so lately as 

 not yet to be parted by a cell-wall from its mother cell, but of which 

 the upper part, st, is already in the act of transforming itself into a 

 spore. *) This circumstance is still more evident in such rather rare 

 and very short branches, as are wholly transformed into spores, so called 

 sessile spores. I have found those mostly in P. Cleveana nob., but 

 also in P. kewensis nob. (pi. 2, fig. 2 ss) and P. polymorph,® nob. (pi. 

 1, fig. 17 ss) . 



As we have found from the exposition given above, the increase 

 in length of the series of cells is produced by the activity of the top 

 cells; while the formation of branches is effectuated by the inclosed 

 cells. Here the following remarks may be made. Bipartition of the 

 cells inclosed in the series occurs now and then. Thus, the cells marked 

 p and b in pi. 3, fig. 1 are daughter cells of an inclosed cell. Neither 

 is the formation of branches from top cells without an instance. Fertile 

 specimens of small size of P. Cleveana nob. are not unfrequently found 

 with not only one, but even two branches developed from the terminal 

 cell of the principal filament, which has then also developed a spore in 

 its top (pi. 2, fig. 13; pi. 4, fig. 16). Of P. polymorpha nob. I have found 

 one specimen, the one represented pi. 1, fig. 17, where two terminal 

 cells, one belonging to the principal filament, the other to a branch, 

 show a beginning ramification (both the branchlets will here consist of 



') In the further process of the development a parting wall will be formed 

 here first at ba' } and afterwards, when the whole chlorophyllaceous mass of the branch 

 cell has passed into the widened part of the cell, at ba". All this being done, the 

 original mother cell will form a spore in its top. Compare pi. 2, fig. 3 st, and pi. 

 5, fig. 4 st. 



