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PACIFIC SCIENCE, Vol. XVII, October 1963 
and auxiliary cells have not been found. Thus, 
though for the present Gibsmithia seems cer- 
tainly to be a member of the Dumontiaceae as 
this family is circumscribed by Kylin (1956), 
the description of the sexual reproduction and 
discussion of the systematic disposition within 
the family are of necessity brief. 
The seirospores are borne in unbranched 
chains at the tips of the exterior filaments in 
the asexual material. At some place along a 
branch bearing seirospores (B in Fig. 5) the 
chromatophore and central vacuole disappear 
rather abruptly and the cytoplasm ( after killing 
in Karpetchenko’s seawater fluid) is then more 
densely granular and with a refractory body 
becoming conspicuous as the cells age. The 
spores, which are about 9 ^ in diameter, appear 
to become more spherical with maturity, as in 
Seirospora. Their ultimate fate is unknown, but 
they are broken off easily in preserved material 
and presumably in nature. 
The subspherical tetrasporangia appear on 
the more basal portions of scattered external 
filaments similar to those bearing the seiro- 
spores. They are, for the most part, in acro- 
petalous series (Fig. 6) on the adaxial side 
of the filaments on which they are produced. 
In a few cases immature tetrasporangia were 
seen below an otherwise acropetalous series. In 
some instances what appeared to be chromo- 
some groups undergoing meiosis were distin- 
guished within immature tetrasporangia. The 
tetrasporangia are apically dehiscent, as in 
Antith amnion, and at least the terminal sporan- 
gia were pedicellate. The first division of the 
cytoplast in the tetrasporangium (Fig. 7) is 
near the equatorial plane. Usually the tetra- 
spore pairs are at right angles to each other, 
i. e., decussately cruciate (Figs. 8, 9); only 
rarely is a somewhat tetrahedral (Fig. 10) or 
other ( Fig. 11) arrangement seen. The tetra- 
spore groups in the collection 12343 are often 
as long as 25 or 30 /i in their major dimension. 
The maturing cystoearps, when stained, ap- 
pear as dots in raised asymmetrically placed 
welts (Figs. 1, 2) near the tips of the branches. 
The largest thalli collected, 10386, were be- 
lieved to be sterile until smears made of the 
branch tips were examined. When this was 
done what are accepted as carpogonial branches 
(Figs. 12-14) bearing nonfertilized carpogonia 
were found. 
The carpogonial branch of Gibsmithia is the 
terminal portion of a modified member of the 
two lateral branch systems arising (Fig. 13) 
from a cell in a medullary filament. Upon oc- 
casion both lateral branch systems bear carpo- 
gonia; less frequently only one of the mem- 
bers is carpogonial, and the other is vegetative 
but reduced in its development. Only mono- 
carpogonial branch systems have been seen. 
Branching from the cells below the special 
cells of the carpogonial branch is variable. In 
some cases there are no such branches (Fig. 
12), and in others (e. g., Figs. 13, 14) up to 
three branches of one to six small cells each 
occur. The cells of these branches, except for 
size, are of the same appearance as the homol- 
ogous cells in vegetative branches nearby. 
The carpogonial branch itself is consistently 
composed of five cells ( cp, a, b, c, and d in Figs. 
12-14), though the terminal carpogonium is 
(Fig. 14) not always present. The antepenulti- 
mate cell (b in Figs. 12, 13) is smaller than 
the other hypogynous cells. Its contents are 
often of different appearance and it is flattened, 
so that its axial length is noticeably less than 
its diameter. The other three hypogynous cells 
are more spherical, similar in content, and the 
largest one (c in Figs. 12, 13) is usually about 
9 to 13 v in diameter. The remaining two 
(a, d in Figs. 12, 13) are usually similar in size. 
The carpogonium is borne on the first 4 hypo- 
gynous cell excentrically, often by a displace- 
ment from the axis of the carpogonial branch 
of about 45 degrees. The carpogonium {cp in 
Figs. 12, 13) is usually relatively small and 
does not stain strongly in aniline-blue, in con- 
trast to the other cells of the carpogonial branch. 
In the material available, stages were not 
found which would enable a satisfactorily com- 
plete description of sexual reproduction. How- 
ever, my impression is that the heavily aniline- 
blue stained condition of almost all carpogonial 
branches seen is a result of development be- 
yond the fertilizable point. Most such branches 
consist of either only the cells a through d ( Fig. 
14) or have in addition what are interpreted 
as remnants of a carpogonium. Such carpo- 
gonial branches are relatively straight and not 
