30 



Veit Beeches Wittrock. 



here changed the bicellular rhizoid into a quadricellular). If the rhizoid 

 has once commenced to increase further, it not seldom happens that it 

 does not stop at the bicellular stage. By apical increase and by divi- 

 sion of the terminal cell, according to the same rule as in the cauloid, 

 rhizoids 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 cauloid. Only in extremely rare excep- 

 tional cases the rhizo'id cells have the power of ramifying. As I have 

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

 to P. Jcetvensis nob. — with a ramified rhizoid; 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 cauloid. 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 rhizoid, which is opposite to that of the cauloid. That 

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

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

 cauloid (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 rhizoid, is, that in such sterile specimens 

 of P. Icewensis nob. as have had the lower part of their cauloid broken 

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

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

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

 rated by bipartition as an individual cell 1 ) (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 words the germination of the prolific cells 

 and the increase of the young plant formed by them. By 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 manner a short cell is often formed upwards, if the upper 

 part of the cauloid is broken oil' in a plant ; see pi. 2, fig. 7 at. 



