The Structure and Reproduction of Gulsonia annulata 
Harvey (Rhodophyta) 
Elise M. Wollaston^ and H. B. S. Womersley^ 
Gulsonia Harvey is a little-known mono- 
typic genus of red algae which has been vari- 
ously placed in the Cryptonemiaceae (Harvey, 
18555 1860), dose to Crouania ( J. G. Agardh, 
1876; Schmitz, 1889) and to Wrangelia (J, G. 
Agardh, 1894, 1897), and in the Nemalion- 
ales near Batrachospermum (Schmitz and 
Hauptfleisch, 1897; Fritsch, 1945). 
Gulsonia annulata was originally described 
by Harvey (1855) from Phillip Island, West- 
ern Port, Victoria and later (Harvey, I860) 
recorded from Georgetown, Tasmania. Har- 
vey’s collections were apparently sterile, but 
later J. G. Agardh (1894, 1897), and Schmitz 
and Hauptfleisch (1897) described carpo- 
spores, tetraspores, and monospores without 
indicating the source of their material. Only 
in recent years has the alga again been re- 
corded (Womersley, 1948, 1950). 
During February, 1956, abundant drift ma- 
terial was collected at Pennington Bay, Kan- 
garoo Island, by the authors. Some 90 speci- 
mens were collected as they were washed in 
over the reef, comprising 51 tetrasporic, 24 
female and cystocarpic, 3 male, and 12 
sterile plants. 
Gulsonia annulata is also known from Sturt 
Bay on Yorke Peninsula and from Eucla, near 
the South Australian-— Western Australian 
border. Apparently it is comparatively rare, 
only being found in drift material from well 
below low tide level; the plants decompose 
fairly rapidly when cast ashore. 
The following account is based on the rich 
Kangaroo Island collection of February, 1956. 
Shortly before this paper was submitted for 
publication, Kylio’s (1956) account of the 
^ Department of Botany, University of Adelaide, 
South Australia. Manuscript received June 4, 1957. 
Rhodophyta became available. Here Kylin 
also recognises the identity of Gulsonia Har- 
vey and Crouaniopsis ] . and G. Feldmann, and 
transfers C annulata (Berthold) J. and G. 
Feldmann to Gulsonia as G. mediterranea Kylin 
nom. nov. The same epithet had also been 
adopted for the Mediterranean species by the 
present authors. Kylin, however, gives little 
more than a formal generic description of 
Gulsonia^ and his comments are apparently en- 
tirely based on the Mediterranean species. 
VEGETATIVE FEATURES 
The plants ranged up to 30 cm. in height 
with an average of 18 cm., and a main axis di- 
ameter of 2 mm. The thallus axis and branches 
are terete, uniaxial, and articulate, with each 
axial cell bearing from its upper end a whorl 
of four short branches of limited growth. 
These whorled lateral branches form nodal 
bands, less distinct in the youngest parts, 
where they almost completely cover the axis, 
and most prominent over the rest of the plant, 
except in the oldest parts of the main axis and 
branches where they become obscured (Fig. 
1). This is due to the development of 1-3 
descending corticating filaments from the 
basal cell of each short branch, which cover 
the axis and in the oldest parts of the plant 
form a dense, tough, and feltlike covering 
over the whorled laterals as well as the axis. 
The corticating filaments are simple or spar- 
ingly branched, of 7-10 elongate cells averag- 
ing 250-300 IX long, by 25-30 /x broad. The 
axial cells of the thallus are approximately 
twice as long as wide, reaching dimensions of 
1300 ju by 700 /x at the base of the plant. The 
intercellular connection between cells shows 
a prominent, thickened platelike structure 
(Fig. 2c, d). 
55 
