398 
2. Cell-fusions. Secondary pits in the cell-walls have not been observed in any 
of the Danish species of Ceramiaceæ. Cell-fusions like those occurring in many 
Cryptonemiales (comp. part II p.279) have only been met with in Rhodochorton 
penicilliforme, where they take place between cells belonging to different rows it 
the basal disc. I have further in a single specimen of Callithamnion Furcellarie met 
with a few cases of fusion between two contiguous cells of the same filament, 
consequently between cells which were before connected by a central pit in the 
transversal wall (fig. 264). As this sort of fusion was only observed in one specimen, 
it must certainly be regarded as an abnormal process. 
3. Hyaline unicellular hairs (comp. K. R. 1911) occur normally in almost all 
the species of Ceramium, in Callithamnion Brodiæi and C. corymbosum; they are only 
wanting in winter when the growth has ceased. They occur often in Plumaria elegans, 
sometimes in Spermothamnion repens and Callithamnion Furcellariæ, rarely in C. roseum 
and Seirospora Griffithsiana, never in Trailliella intrieata, Callithamnion Hookeri and 
C. tetragonum, further in the species of Antithamnion and Rhodochorton.' In Ptilota 
plumosa they occur only at the ends of the branches which surround the procarps. 
4. The number of the auxiliary cells is usually constant. In Callithamnion 
there are normally two. one on each side of the carpogonial branch. In C. Fur- 
cellariæ and C. roseum, however, there is often only one auxiliary mother-cell, namely 
that which gives rise to the carpogonial branch. 
5. The sporangia are lateral, sessile, or terminal on short branchlets. In C. 
Hookeri only have I as a rare exception found intercalary sporangia. In Trailliella 
intricata the sporangia are cut off by longitudinal division of the ordinary cells, a 
mode of formation which is not known in any other filamentous Ceramiacez; it is, 
however, doubtful, whether Trailliella belongs really to this family. The sporangia 
are usually 4-parted. 2-parted sporangia occur in Callithamnion Furcellarie and 
Seirospora Griffithsiana besides 4-parted, but in different plants. In the last-named 
species, however, a small number of tetrasporangia were met with on a plant with 
disporangia. 
The division of the tetrasporangia is either rectangular or tetrahedrical (“tri- 
angular”). In Antithamnion, Rhodochorton and Trailliella the sporangium is first 
divided by a transversal wall in two cells which afterwards are divided by vertical 
walls, perpendicular to the first wall. In the greater part of the Danish Ceramiaceæ 
(Spermothamnion, Callithamnion, Seirospora, Plumaria, Ptilota) the division is tetra- 
hedrical, the sporangium after the quadripartition of the nucleus being divided by 
six walls meeting in the centre of the sporangium. In Ceramium the division is 
variable, now triangular, now rectangular, and the two modes of division may occur 
in one and the same species: but, as shown above, the division of the cell begins 
only after the accomplishment of the nuclear division, and the rectangular division 
in Ceramium is thus a true quadripartition, while that in the three first-named 
genera is established by two consecutive bipartitions. 
* Kuckuck once met with a hyaline hair in Rhodochorton membranaceum (1897, p. 17). 
Re ee menden nn mn 
