Lewis. — The Life History of Griffithsia Bornetiana. 653 
cells by the centripetal growth of a cellulose ring such as occurs in the 
division of certain vegetative cells. 
The rhizoids so formed attach themselves to any neighbouring object, 
curving around it in the manner of a tendril (Fig. 45). In this way the 
plant is more securely anchored than it would be by a holdfast alone. 
Further, rhizoids frequently become entangled among neighbouring filaments 
of the same plant, thus binding the lower parts of the filaments more 
closely together and rendering them less easily torn apart (Fig. 46). This 
is especially true of the antheridial plants, in which the rhizoids are very 
richly developed. 
After the rhizoids become attached, new shoots may arise from them 
in the same way that lateral branches arise from the vegetative cells. 
Tendrils have been known in the red algae since Agardh (1) first 
described them in Hypnea , Mychodea , Rhabdonia, and other genera. 
Setchell ( 71 ) described tendrils in Laurencia and Cystoclonium , and stated 
that they may also serve for vegetative propagation. Nordhausen ( 57 ) 
described tendrils in Hypnea , Spyridia, and Nitophyllum and showed that 
new plants may arise from root-tendrils in Hypnea. 
A species of regeneration occurs in the filament when, as is often the 
case, one of the old cells perishes. Continuity of the filament is re- 
established in the following way : An outgrowth from the cell next above 
pushes through the intercellular pore, and grows down into the cavity of 
the dead cell. The outgrowth is a tube, similar in appearance and mode 
of formation to a rhizoid. The cavity of the outgrowth is perfectly 
continuous with the cavity of the cell from which it originates. A similar 
tube grows up more slowly from the cell below, and the two meet near the 
centre of the old cell cavity (Figs. 47, 48). They fuse at their tips (Fig. 49) 
to form a continuous hollow cylinder; the cylinder increases in size and 
comes to replace the dead cell exactly. The usual intercellular connexion 
is formed at the junction of the new cell with each of the two old cells 
which contributed to its formation. A similar process of regeneration was 
described for Griffithsia Corallina by Janczewski ( 43 ), with this difference, 
however, that in G. Corallina only the cell above the dead cell plays a part 
in the formation of the new cell. Tobler ( 83 ) has shown that a similar 
process takes place in other species of Griffithsia and in Bornetia. 
This process leads at times to the production of a cell of very peculiar 
appearance. When the cell next below two branches perishes, the lowest 
member of each branch puts out a tube (Fig. 47) which meets the tube from 
the cell below. The three fuse at the point of contact and a Y-shaped cell 
results, which is a product of the fusion of three distinct cells (Fig. 50). 
Griffithsia may be anchored to the substratum either by a special 
attaching disk, or more usually by a tangled mass of rhizoids. An attaching 
disk has been noted in plants growing on Zostera and smooth rocks, but 
