652 Lewis . — The Life LTislory of Griffthsia Bornetiana. 
ends of the long cells are seen accumulations of cytoplasm, in which most of 
the nuclei lie. 
The fully formed hairs may remain a considerable time before elonga- 
ting. Elongation occurs in all the hairs of a single node at the same time, 
and seems to take place rather suddenly. The total length of a hair of 
average size before elongation is about 40 /x, and after elongation about 
350 jx. Such great increase in size in a short time seems to be rendered 
possible by the fact that the cells of a hair do not secrete a cellulose wall 
until after elongation has taken place. 
After elongating, the hairs remain for a while on the plant, but finally 
the connexion between the basal cells and the vegetative cell breaks, and the 
hairs fall off as a whole. Not infrequently a second crop of hairs is formed 
before the first crop falls off, so that there appear to be c two sets of hair-like 
organs ’ (Farlow, 29 , p. 132). By the time the second set is formed, the first 
set is carried by the growth of the vegetative cell to some distance from the 
cross-partition between the vegetative cells, and the second set of hairs 
is always formed between the cross-partition and the first set (Figs. 42, 43). 
Individuals vary greatly in the number of hairs produced. In some 
specimens, hairs are found on almost every node in the younger portion of 
the plant. Again, one may look over a great many shoots before 
encountering a single set of hairs. What external conditions are favour- 
able to the production of hairs in Griffithsia is not known. 
In the material examined by Miss Smith ( 73 ), hairs occurred on the 
female plant only on nodes bearing cystocarps. Such a restricted distribution 
is not general. Any of the young vegetative cells seems to be capable of 
producing hairs, and while hairs occur usually in the vicinity of reproductive 
organs, there seems to be no necessary connexion between the two. 
The function of the hairs is quite unknown. They undoubtedly 
increase markedly the surface exposed to the water, and inasmuch as they 
occur especially abundantly in the neighbourhood of the reproductive 
organs, where the processes of metabolism may be assumed to be most 
active, and are usually absent on the sterile portions of the plant, it seems 
likely that they perform the functions of absorption and respiration, as is 
believed by Rosenvinge ( 65 ) to be the functions of similar organs in the 
Rhodomelaceae. 
Rhizoids are frequently formed from the older vegetative cells. Proto- 
plasm accumulates at a spot on the lower half, or near the middle, or even 
at times on the upper half of the cell, and pushes out as a hollow tube with 
a plug of protoplasm at its tip (Fig. 44). In the cytoplasm of a rhizoid the 
chromatophores are rather few in number, and the nuclei are smaller than 
usual in vegetative cells. The average diameter of a rhizoid is about 80 1 u, 
the length 2 mm. or more. The rhizoid secretes a rather thick cellulose 
wall. The longer rhizoids become divided into two or three long cylindrical 
