1906] SIMONS—SARGASSUM FILIPENDULA 169 
Pelvetia jastigiata several epidermal cells cut off basal segments which 
divide transversely until six or more tiers are formed. Over these 
tiers, one or more epidermal cells break down and a cavity results, 
which is gradually enlarged by further disintegration of epidermal and 
meristematic cells. After a time this process ceases, and a “healthy 
surface”’ is formed from the deeper meristematic cells. This surface, 
which comprises the walls of the conceptacle with the exception of the 
upper part that is formed by “cortical rows”’ of cells, produces sexual 
organs and paraphyses. The prominent features which distinguish 
the conceptacle of Pelvetia from others, as thus described, are the 
presence of several epidermal or initial cells, the more extended disin- 
tegration of tissue, and a difference in the behavior of the basal cells. 
The development of the conceptacle in Sargassum filipendula is at 
variance with all the prominent characteristics in the development 
of the conceptacle as described by Bower. The initial cell of Sar- 
gassum does not break down. It is an active cell which produces the 
entire conceptacle. As the whole conceptacle is the product of this 
one cell, adjacent cortical tissue takes no part whatever in the devel- 
opment of the structure. The first indication of the conceptacle is a 
clearly differentiated epidermal cell which lies near the apical cell of a 
reproductive branch (jig. 7) and constitutes the initial cell of the con- 
ceptacle. The upper portion is surrounded laterally by epidermal 
tissue, whereas its central and basal regions are bounded by cortical. 
The initial is much larger than any of the cells with which it is in con- 
tact and differs much from them in shape. Though it may vary some- 
what in length it is always flask-shaped. Its oval bowl, sometimes 
slightly narrowed at the base, tapers above into an elongated neck 
whose outer end is flush with the surface. The initial cell is circular 
in cross section at its apex (fig. ra) and elliptical at its base (fig. 1b). 
The initial cell never breaks down. On the contrary the develop- 
ment of the conceptacle is initiated by its activity. Its large nucleus 
divides. Then a curved wall is formed with concave surface above, 
separating two very unlike cells (fig. 2), which form the two-celled stage 
of the conceptacle. The upper cell, which may be designated the 
tongue cell, is a long somewhat cylindrical structure; whereas the 
lower is somewhat conical or wedge-shaped. The initial cell and the 
two-celled stage of the conceptacle have similar outlines both in longi- 
