6j6 Lewis . — The Life History of Grijfthsia Bornetiana. 
When the stage just described is reached there seems to come 
a natural pause in the life-cycle. In a state of nature a great many more 
sporelings are found in the 3-celled stage than in any other, indicating that 
this stage occupies a longer time in the course of development than any 
other. Under laboratory conditions the 3-celled stage is retained at least 
several days, and frequently development goes no further. The factor 
determining further development seems to be, in part at least, the character 
of the substratum. In the cultures examined it was found that on glass or 
on clean, though rough stones, the basal cell continued to elongate, though 
without further division of the apical cell, until the whole sporeling lost its 
natural colour and died. However, in case the elongating basal cell came 
in contact with some soft substance, it fastened itself immediately, and 
normal development proceeded. In a state of nature, young sporelings of 
Griffithsia have been most commonly found at Wood’s Hole on Champia 
parvula and on Lomentaria uncinata , though they occur on other algae and 
on Zoster a marina. Young plants were sometimes found on stones, the 
surface of which appeared clean, but proved, on careful examination, to 
bear other sporelings, to which the plantlets of Griffithsia were probably at 
first attached. There is no evidence of parasitism, however, in the early 
development of Griffithsia. Sporelings flourish on any soft substratum, 
such as bits of cotton cloth. From the observations noted above, it seems 
clear that Griffithsia Bornetiana needs some other substratum than the 
stones on which the mature plant is often found, to pass through the early 
stages of its existence. 
When the sporeling is growing on some other alga, the basal cell may 
simply become attached to the surface by some adhesive at the surface 
of contact (Fig. 1 52), or may grow in between the cells of the algal 
substratum (Fig. 153), or may even twine about it in the manner of the 
rhizoidal tendrils. 
Further development of the basal cell results in its division into cells 
of various sizes and irregular shape. Usually short tubular projections 
resembling rhizoids become cut off (Fig. 1 54) by the circular ingrowth 
of the cell- wall. Somewhat less frequently dome-shaped segments are 
formed on the sides of the basal cell (Fig. 1 55). In either case a multi- 
nucleate holdfast, or attaching disk is formed, all the cells of which are 
derived from the division of the basal cell (Fig. 156). 
The apical cell cuts off daughter segments in the usual manner 
(Fig. 157). By the time the sporeling is four or five cells long, lateral 
branches appear on the upper borders of the cells below the apex (Fig. 158). 
The rapid growth of the lateral branches gives the characteristic false 
dichotomy to the young thallus. Branching is profuse near the base of the 
sporeling. Frequently five or six lateral branches are given off from each 
of the lower cells, so that the young plant is copiously branched. In this 
