4 Nr. 2. L. KOLDERUP ROSENVINGE: 
sidering the nemathecia, no organs of reproduction are 
known in the genus as founded by SCHMITZ; sex organs 
and cystocarps are entirely unknown. I can confirm this 
for the common European species A. plicata (Huds.) Fries 
of which I have examined numerous specimens from the 
Danish waters gathered in all seasons without detecting 
any trace of reproductive organs besides the nemathecia. 
As the nemathecia have no parallel within the Floridex 
and as they have been variously interpreted, a closer ex- 
amination of their structure and development is needed. 
2. Earlier Investigations on the nemathecia. 
The nemathecia of Ahnfeltia plicata seem to have been 
early observed, but it cannot always be seen from the short 
descriptions of the earlier authors whether the tubercles 
mentioned by them refer to the nemathecia or to the fre- 
quently occurring warts of vegetative character. The lower- 
most tubercle depicted in English Botany tab. 1089 (1803) 
agrees well with the nemathecia and undoubtedly represents 
such an organ. LyNGBYE mentions (1819, p. 42) that the 
tubercles are in particular met with in spring, which is in 
good accordance with the behaviour of the true nemathe- 
cia; he did not observe any spores. C. AGARDH (1822, p. 313) 
names them nemathecia and states that they are composed 
of articulate filaments. The following authors (GREVILLE, 
Harvey, J. AGARDH) confirm that and declare that they 
have not observed any spores, especially no tetraspores. 
KirzinG (Tab. phyc. 19, tab. 66) pictures a section through 
a nemathecium and, more enlarged, the radiating filaments, 
which are said to be composed of “Kettensporen”. They 
are represented as long rows of very small oblong cells of 
