On the PiTHOPHOEACEiE. 15 



spore in its lower eud instead of the npper. Instances of this proceed- 

 ing I have fonnd in P. kein'iisis nob., but particuLnrly in P. Cleveana 

 nob. Two cases belonging to this category I have represented pi. 4, 

 fig. 3 and pi. 3, fig. 8. In the formei case, the cell marked mc has 

 formed first a normal apical spore .s, and afterwards an accessorial basa] 

 spore, sh. The cell just below has also formed a spore, s, in is top; 

 thus this one and the basal spore of the upper cell are made to lie 

 immediately beside each other, thus forming a pair of seeming twin 

 spores. In the latter case, a lower cell has formed two apical spores, 

 .§', s" (but which have received only an incomplete parting wall between 

 them), whilst the upper cell has formed an accessorial basal spore sh; 

 therefore, three spores are here made to lie beside each other, thus form- 

 ing a group of seeming triple spores. 



In P. Cleveana nob. the formation of basal spores besides or 

 instead of apical is not at all uncommon. Especially it often happens 

 in specimens where no rhizoïd has been developed, that the very lowest 

 cell of the thallus, brought forth immediately by the germinated spore, 

 forms a spore in its basal part (pi. 2, fig. 13 sgh^ and pi. 4, fig. 12 sgh). A con- 

 sequence of this is the remarkable circumstance, that the spore formed in this 

 manner has quite the same place as the original mother spore of that 

 plant, and that it even possesses, except at its upper end, exactly the 

 same cell-membrane as the mother spore of the plant. This piece of 

 membrane will consequently, according to the nature of the germination 

 (see »Germination and Increase»), have belonged to three different indi- 

 A'iduals in succession, viz. l:o the one which has formed the spore which 

 has, by its germination, given existence to, for instance, the specimen 

 represented pi. 2, fig. 13; 2:o the individual represented by that figure; 

 and 3:o the specimen which the basal spore will form in future, when 

 germinating. If it comes to pass (as it probably does sometimes), that 

 one specimen after another, Avithout forming a rhizoïd, forms a spore 

 at the lower end of the plant, the same piece of cell-membrane will 

 enter, as a living part, in a whole series of individuals. This circum- 

 stance has seemed to me the more remarkable, because it does not exist 

 in any other pluricellular plant, as far as I know. 



Only in P. kewensis nob. I have had opportunity to. make obser- 

 vations on the order in which the spores are formed. Generally it is 

 basipetal, i. e. the top cell in the principal filament or in a branch first 

 forms a spore, then the cell just below forms one, and so on in a down- 

 ward direction; pi. 2, fig. 5 and fig. 3, 4 .?/'. Deviations from this order 



