Gulsonia annulata — Wollaston and Womersley 
61 
Fig. 4. Three stages in carpospore development. 
Sterile filaments from the axial cell immediately below 
the fertile axial cell form a loose involucre around the 
carpospore mass. 
thallus construction, method of reproduction, 
and arrangement of the carpogonial branches 
are typical of the group. However, Gulsonia 
does differ from Crouania in two important 
features : 
1. The carpogonial branches are borne on 
special fertile branches, whereas they are 
borne on the main axis in Crouania. 
2. Lateral branches of unlimited growth are 
formed from the basal cell of a lateral whorl 
branch of limited growth, whereas in Crouania 
they develop directly from cells of the main 
axis. 
These differences clearly indicate that Gul- 
sonia is genetically distinct from Crouania. 
In 1940 J. and G. Feldmann separated 
Crouania annulata Berthold (a Mediterranean 
species) as a new genus Crouaniopsis, distin- 
guished from Crouania by the same two fea- 
tures as distinguish Gulsonia. This separation, 
and J. and G. Feldmann’s account of Crouani- 
opsis (see also Feldmann-Mazoyer, 1940) in- 
dicate that Crouaniopsis is genetically identical 
with Gulsonia as has been recognised by Kylin 
(1956). In describing Crouaniopsis, Feldmann- 
Mazoyer (1940: 279) compares it with Gul- 
sonia, noting the vegetative similarity of the 
two genera, but follows the description given 
by J. G. Agardh (1894) of the reproduction 
of Gulsonia and assumes the two to be genet- 
ically as well as specifically distinct. Agardh ’s 
description is quite inadequate to indicate 
whether or not the two are genetically dis- 
tinct. The main features of Gulsonia (including 
Crouaniopsis) may be summarised as follows: 
1. Thallus of uniaxial construction with 
short branches of limited growth in whorls of 
four from the upper part of each cell of the 
central axis, giving a noded appearance. 
2. The development of young lateral 
branches of unlimited growth from the basal 
cells of the whorled laterals. 
3. Four-celled carpogonial branches pro- 
duced on special lateral branches which cease 
further development. 
4. A short, loose involucre of filaments 
produced from axial cells at the base of the 
carposporophyte. 
5. A loose cortication of the lower parts of 
the plant by filaments produced from the 
basal cells of the whorled laterals. 
Gulsonia annulata Harvey and Crouaniopsis 
annulata (Berthold) J. and G. Feldmann are 
remarkably similar in form and appearance, 
but (judged from Feldmann-Mazoyer’s fig- 
ures and description) differ as follows: 
Fig. 3. Gulsonia annulata. Stages in the development of the carposporophyte: a, Young four-celled carpogonial 
branch and supporting cell borne on axial cell of a fertile branch; b, trichogyne developing from the fourth 
(carpogonial) cell of the carpogonial branch; c, fusion of spermatia with fully developed trichogyne; d, stage 
after fertilization. Carpogonial cell divided and auxiliary cell cut off from upper face of the supporting cell; e, 
small connecting cell cut off from inferior carpogonial cell and elongation of auxiliary cell towards it; f, con- 
necting cell fused with auxiliary cell while still attached to the inferior carpogonial cell; g, further fusion of 
connecting cell with auxiliary cell now completely separated from carpogonial cell; h, fusion cell (old auxiliary 
cell plus connecting cell) divided transversely to give an inferior foot cell and a superior central cell; i, first goni- 
molobe developed from central cell; j, first divisions in carpospore development from gonimolobe; k, further 
development of carpospores from gonimolobe; 1, a second gonimolobe bud developing from central cell, while 
first bud continues further carpospore development. 
