Gulsonia annulata — Wollaston and Womersley 
59 
or fourth axial cell (from the base) of the 
fertile branch bears two carpogonial branches, 
while the cell above it (fourth or fifth) bears 
one (Fig. 2g). Carpogonial branches have, 
however, been found on axial cells up to the 
seventh, and occasionally four or five on one 
fertile branch. Only one carpogonial branch 
on each fertile branch ultimately gives rise to 
a mature carposporophyte; in fact, not more 
than one mature carpogonial branch with a 
trichogyne was ever observed on a single 
fertile branch. 
An axial cell cuts off laterally a supporting 
cell of similar size (though later the axial cell 
is usually larger), which in turn gives rise to 
the first three cells of the carpogonial branch. 
At this stage the supporting cell and carpo- 
gonial branch are together about 50 /x long. 
The third cell of the carpogonial branch cuts 
off a fourth, the carpogonium which devel- 
ops the elongate trichogyne (Fig. 3a, b). The 
trichogyne projects through the whorled lat- 
erals of the thallus, reaching a length of up 
to 350 M (Fig. 3c). 
Several spermatia may adhere to one tri- 
chogyne, but only one develops a connection 
through the trichogyne wall. Very soon after 
fertilisation the trichogyne disintegrates, leav- 
ing the four-celled carpogonial branch. 
On the upper side of the supporting cell a 
rounded auxiliary cell is cut off, and almost 
simultaneously the fertilised carpogonium di- 
vides transversely to form a small superior 
cell and larger inferior cell (Fig. 3d). From 
the lower part of the latter a small cell (” con- 
necting cell”) is cut off which enlarges and 
grows out towards the auxiliary cell. The 
auxiliary cell elongates to meet the connecting 
cell and ultimately fuses with it (Fig. 3e-g). 
The zygote nucleus presumably is left in the 
inferior cell when the carpogonium divides 
and transferred via the connecting cell to the 
auxiliary cell. The other cells of the old 
carpogonial branch commonly contain more 
than one nucleus at this stage. The first, and 
less frequently the second and third, cells of 
the carpogonial branch may cut off one 
(rarely two) small cells which do not appear 
to have any function (Fig. 3e, f, h). 
Comparatively few stages of actual fusion 
between carpogonium and auxiliary cell were 
found in comparison to large numbers of 
stages just before and shortly after, indicating 
that this transference of the diploid nucleus to 
the auxiliary cell is a rapid one. 
The old carpogonial branch slowly disinte- 
grates while the auxiliary (fusion) cell de- 
velops rapidly. Fusions between the auxiliary 
cell and other cells do not occur, but the 
auxiliary cell divides into a lower foot cell 
and upper central cell (Fig. 3h). The central 
cell buds off successive gonimolobes, each 
cutting off cells which divide to produce 
rounded groups of carpospores (Fig. 3i-l, 
Fig. 4). Only one fairly mature group of 
carpospores is present at any one time, with 
one or two younger groups developing. Ma- 
ture carpospores average 75-80 /x wide by 
100-120 ji long. 
Two or three of the axial cells directly be- 
low those bearing carpogonial branches each 
bear a whorl of di- or trichotomously 
branched sterile filaments, which form a 
short, loose involucre around the carpospores 
(Fig. 4). 
The mature carpospore groups are visible 
as small protrusions scattered irregularly over 
the thallus. The age of the carposporophytes 
shows a steady progression from the younger 
to the older parts of the thallus. On any one 
plant, however, there is not a very great dif- 
ference between the oldest and youngest 
stages present. 
SYSTEMATIC POSITION 
As indicated in the introduction, Gulsonia 
annulata has been variously classified in the 
Cryptonemiales, Nemalionales, and Cerami- 
aceae by different authors. Previous accounts 
of the genus were all limited by inadequate 
material for study. 
This investigation shows that Gulsonia is 
closely allied to Crouania, and belongs in the 
tribe Crouanieae of the Ceramiaceae. The 
