608 
In Lomentaria rosea sex organs are thus far unknown, tetrasporangia only 
are known; but as the species is rather rare, great importance cannot be attached 
to this fact. 
On the other hand, sex organs and cystocarps are the only known organs of 
reproduction in Gigartina mamillosa, whereas tetrasporangia are unknown. It should 
be ascertained whether the sporophyte generation is really wanting or whether 
tetrasporangial sori may perhaps have been confounded with cystocarps. 
Rhodymenia palmata is very remarkable by having tetrasporangia and antheridia, 
whereas carpogonia and cystocarps are unknown. As this species is widely spread, 
it must be supposed that the last-named organs are really lacking, and the spermatia 
must then be without function. As a fertilization does not take place and no other 
mixie has been ascertained, it must be expected at the outset that nuclear division 
in the sporangium does not have the character of a meiosis. According to Miss 
WESTBROOK, a double spireme stage and a synizesis was ascertained by the first 
nuclear division, but the accomplishment of the reduction division has not been 
substantiated, and it may be supposed that this process is only initiated but not 
performed. 
It is interesting to note that there are other Floridex which agree with Rhody- 
menia palmata in having only tetrasporangia and antheridia whereas female sex 
organs and cystocarps are wanting, viz. Antithamnion boreale (Part III, p. 370), 
Rhodochorton penicilliforme (Part III, p. 389), Rhododermis elegans? and Halosaccion 
ramentaceum*. 
In Ceratocolax Hartzii well developed tetrasporangia occur, and the tetraspores 
are undoubtedly able to give rise to new plants infesting Phyllophora Brodiei, though 
the first stages of the germination have not been observed. Sex organs too occur, 
at any rate procarps, which are, indeed, usually badly developed; apparently 
normal carpogonia with long trichogynes may, however, be met with. Antheridia, 
too, seem to be produced but they are scarcely quite normal. And the fact that 
fertilization and cystocarps have never been observed corroborates the supposition 
that the sex organs do not reach a normal development. The tetrasporangia develop 
in (winter and) spring, they are ripe in April and May, and after June tetrasporangia- 
bearing plants are not observed. The individuals as a rule bear either tetrasporangia 
or sex organs, but as, in one case at least, the presence of nemathecia and sex 
organs in one and the same specimen was ascertained, it is probable that this is 
a normal occurrence. It must then be supposed that an alternation of generations 
does not take place here, but that the individuals produce first tetrasporangia and 
later sex organs without normal function. As procarps may arise also in spring, it 
is possible, however, that some individuals produce only sex organs or that these 
organs can be produced independently of the nemathecia. 
* KoLDERUP ROSENVINGE, The Marine Algz from North-East Greenland. Meddelelser om Gron- 
land, Vol. 43, 1910, p. 105. 
* H. Jonsson, Mar. Algæ of Iceland, I. Bot. Tidsk. Bd. 24, 1901, p. 139. 
