12 



Veit Brecher Wittrock. 



cells are more seldom found in purely fertile specimens (pi. 2, fig. 1, 2, 

 3). (On the different kinds of individuals as to the power of repro- 

 duction, the fertile, the half-fertile-half-sterile, and the sterile, see below 

 in this paragraph). At the time when the formation of spores is to 

 take place, the formation of vegetative cells has ceased in purely fertile 

 specimens, and the specimen has consequently attained its full size. 

 All or most cells are then found to be so rich in chlorophyll, that the 

 granules of chlorophyll form a continuous layer over the whole in- 

 side of the cell-wall. The formation of spores is introduced by the 

 upper part of the mother-cell of the spore (in P. kewensis nob. generally 

 Y 3 — 7 4 of the cell) widening a little (pi. 3, fig. 4 «§), so that it does at 

 last assume the form of a rather slender cask; if the mother cell of the 

 spore is a terminal cell, the upper end of the cask is pointed like a 

 cone (pi. 3, fig. 5 s). It is this part of the cell that is to be developed 

 to a spore. As yet, no change in the other part of the cell is percept- 

 ible. But when the widening of the upper part is completed, the gra- 

 nules of chlorophyll in the lower, cylindrical part of the cell commence 

 to pass into the upper cask-shaped part. During this process it has 

 seemed to me as if the parietal layer of chlorophyll were interrupted 

 at the point where the cask-shaped widening of the cell commences — 

 at least I have seen numerous cells during their forming spores, in 

 which the chlorophyllaceous body of the nascent spore has already 

 at an early period been so sharply limited at the lower end, as pi. 3, 

 fig. 6 shows. It is possible that, at this place, only a folding inwards, 

 without a complete interruption of the layer of chlorophyll, has taken 

 place. Be this as it may, at all events the parietal layer in the enlarged 

 part of the mother cell of the spore does not suffer a displacement (for 

 instance in such a manner that the chlorophyll in the lower part of the 

 enlarged space were removed higher up), but, remaining in its original 

 position, it is augmented in thickness by apposition from within, till 

 the whole swollen part of the cell is filled with chlorophyll-coloured 

 protoplasm. The chlorophyll from the lower, cylindrical part of the cell 

 moves into the upper cask-shaped part (pi. 3, fig. 6), at the same time 

 completely filling the space which has been occupied by the great central 

 vacuole of the cell. This requires, as a rule, almost the whole chloro- 

 phyllaceous mass of the cell, so that only a few granules of chlorophyll 

 are left in the lower part (pi. 3, fig. 7). When the whole chlorophyllaceous 

 mass has in this manner been completely removed into the upper and 

 swollen part of the mother cell of the spore, the formation is commenced 



