1906] SIMONS—SARGASSUM FILIPENDULA cy gs 
is cut off by a transverse wall (jig. 24). The lower cell becomes a 
part of the wall occupying the place of the cell from which it arose. 
The upper cell enlarges for a time and then divides, forming the 
sperm mother-cell or spermatocyst and its stalk (jig. 24, at the right.) 
A stalk cell may have no other relation than that which it bears to 
the spermatocyst which it supports, or it may function in other ways. 
It may produce several spermatocysts directly, without individual 
stalks; it may put forth a papilla which gives rise to a spermatocyst 
and stalk (figs. 25, 26); or it may develop a hair (fig. 27). Hairs, 
however, are comparatively rare within a conceptacle of Sargassum. 
Owing to the variety of activities which belong to a stalk cell, the 
growths within a conceptacle lack uniformity. Some structures reach 
but a little distance above the wall of the conceptacle, whereas others 
form conspicuous branch systems. Although these systems are prom- 
inent in this conceptacle, they are considerably smaller and less dense 
than the branch systems in a conceptacle of Fucus, and there is far 
more unoccupied space within the cavity of a conceptacle of Sargassum 
than of Fucus. 
The young spermatocyst contains dense cytoplasm, a centrally 
placed nucleus and deeply staining granules, the nucleus remaining in 
a resting condition for a long period. The divisions of the nucleus 
were not studied in detail. Sixty-four sperms are apparently formed 
(figs. 27 and 28), agreeing, therefore, with the count announced by 
BEHRENS (’86) for Fucus vesiculosus. The sperms within the 
spermatocyst have an elliptical outline, a cytoplasmic ground mass, 
and a somewhat spirally arranged band, which is probably the nucleus. 
The discharge of sperms was not seen, but a rent, partly terminal and 
partly lateral in empty spermatocysts, indicates their mode of escape. 
THE OOCYST. 
The female sexual organ (oogonium) or oocyst, according to the 
_ terminology of Davis (:04), is peculiar among the Fucaceae, as far as 
is known, in that it is not borne upon a stalk but is a partially embed- 
_ded organ (fig. 31). The sister cell of the oocyst, instead of develop- 
ing into a pedicel cell as is usual in this family, functions as one of 
the wall cells of the conceptacle. The oocyst enlarges greatly, but 
becomes nearly surrounded by adjacent wall cells. 
