bit 
in June at the Farôes (M. A. Fær. 1902, p. 357). The cystocarps arise in the papillæ 
covering the flat frond. The procarps seem not to have been described; I have nol 
observed them, perhaps owing to the fact that I haye only examined specimens 
gathered in late summer (August, September). Ripe and partly emplied cystocarps 
were met with in August. According to the authors (J. AGARDH, Scumirz and Haupr- 
FLEISCH, SJOSTEDT), the gonimoblast is surrounded in the genus Gigarlina by an 
inner pericarp of medullary hyphæ. This pericarp, however, is not represented, 
or only feebly developed in Kürzıng’s figures of this species (1843 and 1867) and 
I have not observed it on the outside of the gonimoblast. As shown by KürziNG 
(1867), transverse secondary pits are very well developed in the inner part of the 
cystocarpial wall exactly corresponding to the inner cortical layer of the frond. 
Ripe and partly emptied cystocarps were met with at Thisted in August. Tetra- 
sporangia are unknown. As they have been searched for by several phycologists, it 
seems most probable that they are really wanting. On the other hand one might 
imagine that they do occur in the papillæ, just like the cystocarps, and that the 
sori of tetrasporangia might have been confounded with the cystocarps, as has been 
the case repeatedly with Chondrus crispus. 
Gigartina mamillosa has up to 1929 only been found in two localities at the 
shores of Denmark, namely at Thisted in the Limfjord and at Aarhus on the east 
coast of Jutland, in both places growing on moles of the harbour or on stony 
slopes near the harbour. As shown in an earlier paper’, it must be supposed that 
it has been introduced into both localities by vessels. As to Thisted, where the species 
was first found by J. P. JACOBSEN in 1869, this conclusion is almost certainly correct 
1) since the salinity of the Limfjord before 1825, when the isthmus separating the 
fjord from the North Sea was broken through, was so slight that is was impossible for 
G. mamillosa to thrive here, 2) since the species has not been found elsewhere in the 
Limfjord and 3) since the part of the fjord (Thisted Bredning) where Thisted is 
situated is connected with the other parts of the fjord only by narrow channels 
with Zostera vegetation. The average salinity in the western part of the Limfjord 
is now 29 p.m. At Aarhus the species was found on a stony slope north of the 
harbour in 1911 or 1912. One might imagine that it might here be a relict from 
a time when the salinity was higher than now, when it varies probably about 
20 p.m.; but that is quite improbable as the species has never been found else- 
where in similar localities in the Samsø waters or in Kattegat (except Skagen). It 
is therefore highly probable that the species has been introduced to this much 
frequented harbour by a vessel. 
Gigartina mamillosa grows at low-water mark, at Thisted under the Porphyra- 
belt, over the Fucus vesiculosus-belt or partially in the upper part of this. It thrives 
well at Thisted, where it reaches a length of 5—8 cm, whereas at Aarhus it be- 
1 Om nogle i nyere Tid indvandr. Havalger i de danske Farvande. Botan. Tidsskr. Bd. 37, 1921, 
p. 126 and 133 (English abstract). 
