412 
THE SEAWEEDS 
S. gracilis J. Agardh is only a slender form of S. 
comosus, and is not recognized by De Toni. 
Same localities as 8. comosus. 
8. radiciformis (R. Br.) C. Agardh. Eastern 
Bays. 
S. scoparius Harvey. Eastern Bays, Encounter 
Bay. - 
P&rithalia J. Agardh. 
P. inermis (R. Br.) J. Agardh. Eastern Bays, 
Encounter Bay. 
Encyothalia Harvey. 
E. Cliftoni Harvey. Eastern Bays, Encounter 
Bay, Investigator Strait. 
It might be expected that Carpomitra mitriformis 
would be found along our coastline, but as yet it has 
not been discovered. 
(iii.) DESMARESTIALES Setchell and Gardner 1925. — Plants 
of filamentous construction, the branches showing sub- 
apical trichotliallic growth, and the filaments developing 
uniaxial branches, often with considerable cortication; 
reproduction by zoospores borne in unilocular sporangia 
from which develop microscopic filamentous oogamous 
gametophytes. There are only three genera in the one 
family. 
Desmarestiaceae (Thuret) Kjellman 1880. Not known 
to be represented here. 
(6) POLYSTICHINEAE (Kuckuck) Kylin 1933.— The sporophyte has 
a parenchymatous thallus produced by vertical and transverse 
division of intercalary cells, growth never being trichothallic ; 
reproduction is by zoospores or aplanospores (neutral spores). 
The gametophytes are microscopic and either isogamous or 
anisogamous. The sub-class is divided into three orders. 
(i.) Punctariales Kylin 1933. — Plants subfilamentous or 
membranous-expanded, with intercalary growth and ulti- 
mately parenchymatous subdivision of the cells; unilo- 
cular sporangia and plurilocular gametangia present, 
also gametes upon the microscopic monoecious gameto- 
phyte. Family subdivision within this order is not yet 
absolutely definite owing to the fact that exact cytological 
studies have not been made upon an indicative scale, 
and Tilden (1935) and Taylor (1937) divide the order 
differently into at least three families. 
Tilden : Scytosiphonaceae. 
Asperococcaceae. 
Coilodesmaceae. 
Punctariaceae. 
