30 Veit EKiiciiicR ^A^ittrock. 



here changed the bicoHuhir rhizoïd into a qiiadricolhihir). If thr rhizo'id 

 has once coninieucod to increase further, it not sekhnu hapjjcns that it 

 does not stop at the bicelhüar stage. By apical increase and hy divi- 

 sion . of the terminal cell, according to the same rule as in the caulo'id, 

 rliizoïds are sometimes formed consisting of several — as much as 12 — 

 vegetative cells (pi. 4, fig. 6, 7). As may be understood by the mode 

 of increase now indicated, they all form a single series of cells, analogous 

 to the principal filament of the cauloïd. Only in extremely rare excep- 

 tional cases the ihizoi'd cells have the power of ramifying. As I have 

 mentioned above (pag. 8) I have found only one specimen — belonging 

 to P. kewensis nob. — with a ramified rhizo'id; see pi. 4, fig. 8. The 

 nature of the branches (which are all of the l:st degree and unicellular) 

 indicates very clearly, that they are formed in a manner quite analogous 

 to that in which the normal branches are formed in the cauloïd. Their 

 attaching point being the lower part of the mother cell, as well as their 

 pointing downwards, are the natural consequences of the direction of the 

 increase of the rhizoïd, which is opposite to that of the cauloïd. That 

 formation of sjDores in rare and exceptional cases may take place in the 

 rhizoïd too, and that it then takes place in the same manner as in the 

 cauloïd (i. e. basipetally, if -more than one spore are formed) has been 

 mentioned before (pag. 16). 



A phenomenon, which may be mentioned together with the ac- 

 count of the formation of the rhizoïd, is, that in such sterile specimens 

 of P. keicen.^is nob. as have had the lower part of their cauloïd broken 

 oft' by some accident, the lowest cell left is not seldom found to elon- 

 gate itself in the direction of the lost rhizoïd, and to form, in this 

 manner, a rhizoïd-like process (pi. 2, fig. 11 rl) which is, at last, sepa- 

 rated by bipartition as an individual cell ') (pi. 2, fig. 12 rl). 



Having completed the account of the germination of the spores 

 and of the increase of the plant to which they have given origin, it 

 remains to describe in a few Avords the germination of the prolific cells 

 and the increase of the young plant formed by them. Bj the destruc- 

 tion of the rest of the plant the prolific cells are made free, not always 

 so that each prolific cell is quite isolated — this occurs, however, now 

 and then — but generally thus, that two or more prolific cells still 

 hang together and form longer or shorter series of cells (pi. 2, fig. 2, 



') In the same inanncr a short cell is often Ibrincd upwards, if the upper 

 part of the cauloïd is broken off in a phmt ; see pi. 2, fig. 7 d- 



