The Botany of Iceland - 01.12.1912, Síða 181

H. JÓNSSON : MARINE ALGAL VEGETATION
167
A. Annual algæ. The annual species are especially the Green
Algæ which grow in the upper littoral zone and are exposed during
each low-tide. The upper littoral zone is that part of the algal region
where the change of seasons is most felt and where winter prevents
many species from continuing life. Such species then produce spores
which live through the winter as such, or in the early stages of
germination. Of annual species the following may be mentioned: —
Codiolum gregarium.
C. pusillum.
Percursaria.
Enteromorpha-species.
Monostroma-species.
Prasiola-species.
Ulothrix-species.
Ulvella.
Pringsheimia.
Urospora-species.
Chætomorpha tortuosa.
Spongomorplia vernalis.
Cladophora-species.
In addition, some of the endophytic species must be regarded
as belonging to the annuals, although some of them can be met
with at all seasons of the year. As examples of such species may
be mentioned: — Chloroclujtrium-s\)eóes and Codiolum Petrocelidis.
The life-periods of the species mentioned above are probably
of different lengths and it is possible that some of them can pro-
duce several generations during one summer (cf. Börgesen, 11
and 12). The majority of these species grow luxuriantly during
spring (March—May) and summer (June—August), produce spores
at the end of summer and then die. Some of tliem, however, con-
tinue life into Ihe autumn (Septemher—November), or at any rate
until September. A few may also be met with during winter (De-
cember—February), e. g. Enteromorpha intestinalis f prolifera, Mono-
stroma fuscum (sterile and fruiting), Cladophora rupestris (abundantly)
and Cladophora sericea (sparingly).
Of the above-mentioned endophytic species I shall refer to
Chlorochijtrium inclusum and Codiolum Petrocelidis only. Both these
species occur at all seasons of the year. They are found most fre-
quently in the host-plants in the sublittoral zone, where the conditions
of life must be considered to be more stable than in the littoral
zone. I regard such species as short-lived. They are found all the
year round, as probably several generations are produced during
the year.
Among the annual Brown Algæ the following must be in-
cluded: — Myrionema-species, Ascoqjclus and the majority of the
Ectocarpaceœ, Leptonema, Litosiphon, Isthmoplea, Phœostroma, Ca-