Pacific Species of Antithamnion — TOKIDA and InabA 
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Fig. 9. Acrothamnion pulchellum J. A g.: a, middle portion of a main branch, showing opposite 
pinnae laterales and secund pinnae transversales; b, lower portion of a frond, showing the mode of 
branching, details of all the pinnae but one having been omitted; c, six pinnulae crowned with apical 
gland cells; d, typical forms of both pinna lateralis and pinna transversalis, on the left side an excep- 
tional pinna lacking the apical gland cell; e, three pinnae transversales, showing the variety of the 
arrangement of pinnulae. a, X 75; b, X 40; c, d, and e, X 150. 
with a gland cell. The occurrence of pin- 
nulae on the rest of the cells of the axes is 
irregular. Although the accessory pinnae are 
as a rule single on each axial cell of branches, 
sometimes they happen to be absent on cer- 
tain axial cells or two may be formed from 
each axial cell. In the latter case, two acces- 
sory pinnae stand side by side on the same 
side of the frond axis. The pinnulae, either 
on the principal or accessory pinnae, are gen- 
