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PACIFIC SCIENCE, Vol. IV, April, 1950 
Fig. 8. Acrothamnion pulchellum J. A g. Spec- 
imen from Shirahama. X 6- 
axes of pinnae 25—30 g diam. at the basal, 
35 g diam. at the suprabasal, and 20g diam. 
at the subapical cells; transverse pinnae se- 
cund, smaller than the lateral ones, 72-280 g 
long, 10-20 g diam., simple or sparsely pin- 
nulate above, in the latter case provided with 
opposite pinnulae on the apical segment and 
sometimes also with opposite or secund pin- 
nulae on the subapical segments; gland cells 
always on the apices of pinnae and pinnulae, 
sitting between the two apical pinnulae on 
two basal cells of either of them, 10-20 g 
high, 20-25 (-30) g diam.; chromatophores 
discoid, numerous. Sexual reproductive or- 
gans unknown; tetrasporangia observed on a 
specimen from Western Australia. 
Japanese name: Kujaku-hanemo (nom. 
nov. ) . 
Specimen: Growing on the thallus of Geli- 
dium subcostatum Shirahama, Prov. Boshu 
T. inaba 351, Mar. 11, 1944 (Herbarium, 
Dept. Fish., Hokkaido Univ.). 
This beautiful species was discovered to be 
partly repent upon the thallus of Gelidium 
subcostatum, being attached by means of 
many rhizoidal filaments issuing from the 
lowermost cell of the pinnae at the lower 
portion of the frond and not uncommonly 
near the apical portion as well. The plant 
stands close to Antithamnion in the charac- 
ters of the growing point and in the method 
of branching as well as in the possession of 
opposite pinnae on each segment of the main 
axis; but on the other hand it differs from 
that genus in having a single dwarf accessory 
pinna or transverse pinna on each axial seg- 
ment of branches in addition to the above- 
mentioned opposite pinnae, and in having 
quite characteristic apical gland cells. The 
branches arise from the lowermost cell of 
either or both of the opposite principal pin- 
nae. The axial segment of branches gives rise 
near the top to three pinnae in all, or two 
opposite larger pinnae and a single smaller 
pinna, of which the latter arises in the direc- 
tion crossing at right angles with the plane 
including the two opposite pinnae. The 
smaller transverse pinnae are secund on one 
side of the main axis which corresponds to 
the side from which branches and rhizoidal 
filaments arise or to the underside of the 
repent portion of the frond. The principal 
pinnae bear two opposite pinnulae, as a rule, 
on each axial cell except the lowermost one. 
The number of the opposite pairs of the pin- 
nulae for one principal pinna ranges from 5 
to 11 (as indicated by our counts of many 
pinnae, amounting to 224 in all). The fre- 
quency of each number was as follows: 
Number of pairs: 5 6 7 8 9 10 11 
Frequency: 1 5 11 47 98 59 3 
As can be seen in the listing above, the pin- 
nae with nine pairs of pinnulae were most 
frequent in occurrence. The spread of two 
opposite pinnulae and that of two opposite 
pinnae measures 90-225 g and 240-690 g 
in width, respectively. The accessory pinnae 
or transverse pinnae, in the typical form, 
bear at least one pair of opposite pinnulae 
on the apical axial cell, which is crowned 
