Algae. 
385 
2. Baltic Sea and Skagerak (G. Swenander). 
3. Danish Seas (C. H. Ostenfeld). 
4. Western Baltic and Eastern North Sea. 
5. South-eastern North Sea (J. P. van Breemen). 
6. Southern North Sea. 
7. The English Channel (W. Bygrave) 
8. North-Western North Sea. 
9. Arctic Sea (Barents Sea). 
The material has been collected during expeditions made from 
Belgium (N°. 6), Denmark (3), England (7), Finland (1), Ger- 
many (4), Holland (5), Russia (9), Scotland (8) and Sweden (2). 
C. H. Ostenfeld. 
Jörgensen, E., Phytoplankton in: 0. Nordgaard, Mofjordens 
naturforhold [The natural conditions of Mofjord]. (Trond- 
hjem, kgl. norske Vidensk. Selsk. Skrifter, 1906, N°. 9, 1907, 40 pp.) 
The Mofjord is the innermost part of a long narrow Norwe- 
gian fjord in the neighbourhood of Bergen. It has a shallow en- 
trance and is inside this rather deep, (217 m. at the deepest place). 
The surface water is rater fresh, but very variable (salinity from 
1 to 20 per mille) according to the amount of afflux of freshwater 
from rivulets. The greatest thickness of this sheet of fresh surface- 
water is about 10—12 m. At a depth of 20—30 m. the salinity is ab. 
30 p. mille, and now the salinity increases slowly towards 60—80 m., 
from where it becomes fairly fixed at 32,2 per mille. The amount of 
gas contained in the water is very peculiar; the amount of oxygen 
decreases from the surface to the depth of 60 m., where it has its 
minimum (0,14 per mille); at the same depth sulphuretted hydrogen 
begins to occur and increases towards the bottom. The result of 
this distribution of gases is, that the water from 60—80 m. towards 
the bottom is practically sterile. 
The plankton-samples show a very rieh phytoplankton in the 
upper layers (0—35 m.), while mostly only empty frustules of 
diatoms and peridinians have been found in the lower ones. The 
dominant species are: Chaetoceras curvisetum, Sceletonema costatum 
and Ceratium spp. A few freshwater forms, viz. Melosira varians, 
Surirella ovata and Tabellaria ßocculcsa have been noted, more or 
less scattered. C. H. Ostenfeld. 
Walker, N., The Algal Vegetation of Ponds. (Rep. Brit. Assoc. 
York. 1906 [1907]. 758, 9. pp.) 
The ponds examined are situated above the Bramhope railway 
tunnel, near Leeds, and occupy excavations in clay which were 
made sixty-seven years ago. The following are the available sites 
for attached algae: 1. Winter shoots of Oenanthe fistulosa. These 
form a pale green zone, from 2—3 yards wide, extending from the 
edge of the pond to a depth of about 9 inches. From September to 
May Tribonema bombycinum Derb. & Sol. dominates, with abundant 
Ulothrix subtilis var. variabüis. In June these disappear and sterile 
species of Zygnema are established, followed by Tolypothvix lanata 
Wartm. In July and August Anabaena oscillarioides Bory is followed 
by OsciUatoria anguina Bory with Phormidium molle Gom. These 
are displaced by O. amphibia Ag. — Site 2. Shoots of Potamogeton 
natans and Sparganium ramosum occurring in the deeper water 
(1—3 feet). In winter species of Oedogonium and Bulbochaete domi- 
Botan. Centralblatt. Band 107.1908. 25 
