Contributions to the Knowledge of the Pacific Species 
of Antithamnion and Related Algae 1 
Jun Tokida and Tadaaki Inaba 2 
The junior author, T. Inaba, expert of 
the Fisheries Department of Fukui prefec- 
tural government, was able to make collec- 
tions of marine algae along the coast of Boso 
Peninsula lying southeast of Tokyo Bay, dur- 
ing the time he was engaged as a teacher in 
the Awa Suisan-Gakko (School of Fisheries) 
in Tateyama City, Chiba prefecture. This is 
a most interesting coast for phycologists, of- 
fering many kinds of temperate-zone sea- 
weeds, and, of course, has already been fre- 
quently botanized by many other persons. 
Nevertheless, further effort in searching there 
for new or rare species seems to be quite 
promising in view of the fruitfulness of the 
junior authors collections, especially those 
made in the spring of 1944. Partial results 
of our studies on the species of Antithamnion 
and its allied genera which were thus discov- 
ered are reported here. 
The text figures la, lb, 4, 5 a, 5 b, and 1 Oa 
are reproduced from the drawings by Inaba, 
while the rest are from those of Tokida. Fig- 
ures 6 and 8 are reproduced from photograph 
negatives obtained by projecting on bromide 
papers with an enlarging camera the images 
of the specimens mounted in glycerine on a 
glass slide. 
It will not be superfluous to give here an 
explanation of the technical terms used in 
our descriptions. By the terms "ramus” or 
"branch,” "pinna,” "pinnula,” and "ramulus ,” 
x The expense of the present study has been 
partly defrayed from the subsidy granted by the 
Hattori Hoko Kai, and from the fund for scientific 
research granted by the Ministry of Education. 
2 Botanical Laboratory, Department of Fisheries, 
Faculty of Agriculture, Hokkaido University, Sap- 
poro, Japan. Manuscript received April 26, 1949. 
we intend to express the different orders of 
the successive branching system in Antitham- 
nion and its allied genera. The ramus, being 
provided with a meristem at its top, is the 
direct offshoot of the main axis of the frond 
and bears pinnae. Pinnae, in Antithamnion, 
are usually opposite or sometimes whorled 
offshoots on each segment of the main and 
branch axes, simple or divided, bearing, in 
the latter case, pinnulae. Pinnulae, in Anti- 
thamnion, are opposite, alternate, or secund 
on the pinnae, arising usually singly or rarely 
by pairs from some segments of the axis of 
pinnae. Ramuli are usually simple offshoots 
arising singly from some segments of the axis 
of pinnulae. By "ultimate ramuli,” however, 
we do not always mean ramuli but sometimes 
mean either pinnulae or pinnae according 
to the extent of intricacy of the branching 
system. 
The senior author wishes to acknowledge 
his indebtedness to Mme. Valerie May for her 
kindness in sending him a fragment of an 
authentic specimen of Acroth amnion pul- 
chellum J. A g., and to Dr. E. Yale Dawson 
of the University of Southern California for 
his kindness in sparing from his library val- 
uable publications helpful for the present 
study. 
Antithamnion basisporum Tokida and Inaba, 
sp. nov. 
Figs, la-c; 2 a-d 
Fronde sparse ramosa et opposite pinnata; 
axibus principalibus inferne repentibus, rhi- 
zoidibus brevissimis et simplicibus, 16-26 g 
crassis, a cellulis basalibus pinnarum emit- 
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