mum, fig. 314) I judged it convenient to examine the division process itself in im- 
bedded proofs of C. diaphanum and C. rubrum, and in both species tetrahedral 
and rectangular division was ascertained in different sporangia of the same plant. In 
every case the division of the nuclei was accomplished before the division began 
(fig. 312 A —C). The division of the cell takes place by walls growing gradually from 
the periphery towards the centre of the cell, but the orientation of the walls is 
variable. In figs. 311 A and 312E are represented typical tetrahedral divisions. In 
other cases a transversal wall is first formed as an annular list 
while two other walls, perpendicular to the first are formed a little 
later but before the first wall is finished (figs. 311 B, 312 D, F, H). 
The division seems thus in all cases to be a division in four of 
one cell and not a bipartition of the spore-mothercell into two cells 
which afterwards divide into two. 
Fig. 313. Paraspores occur in C. diaphanum, C. strictum (comp. HEnn. 
Ceramium diapha- PETERSEN 1908 pp. 51, 85) and C. Deslongchampsii, and I have found 
an SEA a couple of sori of paraspores in a specimen of C. vertebrale which 
390 : 1. bore at the same time tetrasporangia (fig. 323). These paraspores 
were remarkable by peculiar pseudopodia from the protoplast to 
the membrane. The paraspores, as shown by HENN. PETERSEN, develop from a 
superficial cortical cell (fig. 313), often from à marginal cell of a cortical band. They 
never occur in the sexual plants but often in tetrasporiferous plants. 
HENN. PETERSEN states briefly that he has met with a sort of monospores in 
C. diaphanum (1908 p. 14).* 
Key to the Danish species of Ceramium. 
(By HENNING E. PETERSEN). 
1. Cortication only at the nodes; distinct cortical bands. 
2. Gland cells present, outer edge of apex dentate.................... 1. C. tenuissimum. 
2*. Gland cells wanting, outer edge of apex usually even. 
3. Cortical bands usually over 100 4 high, lower border-cells irreg- 
ularly shaped; frond not creeping. 
4. Apices always curved inward. 
5. Cells in the lower edge of the lower bands usually not 
over 13 u in transversal diameter; cortication often much 
developed, bands sometimes upward growing............. 2. C. diaphanum. 
5*. The named cells usually 17—20 u in transversal diameter .... 3. C. strictum. 
4*. Apices always straight. 
5. Bands of about equal height and breadth ........... 5. C. Deslongchampsii. 
5”. Bands usually broader than high; often up to 30—40 axial 
cells between the bifurcations; only in the inner waters ... 6. C. vertebrale. 
' Dr. PETERSEN refers to Gogrs fig. 8 in Die Rothtange des Finn. Meerbusens. Mém. Acad. St. 
Pétersb. XXV No. 7, 1877; but the bodies alluded to in this figure according to the author represent 
tetrasporangia (“Tetrasporen’”) the division of which is not shown. 
