b72 Algae. 



association contains the organisms which oiten occur together, forming 

 on association like that of higher piants. The author distinguishes in 

 the Noiwegian Sea 6 plankton-elements, viz : arctic-neritic, boreal- 

 neritic, temperate - atlantic - n e r i t i c , arctic - oceanic, 

 boreal-oceanic and temperate -atlantic -oceanic, all the 

 species of which are enumerated, the most characteristic being marked 

 out as types. 2. The area oi the Norwegian Sea is divided in plank- 

 ton-regions, viz: a) surface regions: Tripos - r e g i o n from the 

 Fserö-Shetland-deep along the Norwegian coast, Asteria nella - r e g i o n 

 around Zeeland and Clio -r egion in the northern and western part of 

 the area; b) deep-searegions : Euchaeta - r e g i o n in the warmer part of 

 the North- Atlantic current and Cyclocavis- r eg i on in the cold bottom- 

 waters of the area. These regions are characterized with regard to their 

 plankton-elements and associations. 3. Discussion of the importance of 

 the study of the plankton as a controle of hydrography, the result of 

 which is as follows: it is possible to control the hydrographical results 

 with regard to the boundary of the great water-areas ; further the plankton- 

 investigations are often able to distinguish the different components in 

 water-areas of mixed origin. 



Chapt. IV (p. 107—123). The quantitative distribution of 

 the plankton. The author says that the counting method is unpracti- 

 cal and he returns to the subjective judgement as the most simple 

 method. In the surface-layers the phytoplankton is of most importance ; 

 the quantity of the Peridinea (and Halosphaerä) increases proportionally 

 to the light and the temperature and has its maximum in summer; the 

 quantity of the diatoms on the other hand is also dependent on these 

 factors, but has mostly a maximum in spring and an other in autumn. 

 This fact is according to the author to be explained as follows: when 

 in spring the intensity of the light is strong enough for the propagation 

 of the diatoms, this propagation takes place so rapidly that the soluble 

 food-substances are consumed ; during the summer the propagation 

 therefore is proportionate with the quantity of the food-substance which 

 then occurs scarcest, following the minimum-law of Liebig; and this prin- 

 cipal food-substance is probably the nitrogen. 



Chapt. V (p. 127 — 161) is „a summary of the observations arranged 

 according to the stations, together with remarks on the biological 

 character of the water-layers investigated". 



Chapt. VI (p. 162 — 212) is a systematical list containing the obser- 

 ved species with remarks on their distribution, of which in this abstract 

 only the protophytes are of interest. New is Chaetoceras Ingolfianum 

 Ostf. in litt, among the diatoms. Further the author has given a 

 general survey of the northern species of Peridinium and Ceratium, de- 

 scribing the new forms: P. conicum Gran, P. pentagonum Gran and 

 Cerastiwn compressum Gran. 



The plate exhibits the above-mentioned sporulation and the auxo- 

 spores of Rhizosolenia styliformis and development of Halosphaerä 

 viridis. C. H. Ostenfeld. 



ÜAZEN, Tracv ELLIOT, The Ulothricaceae and Chaetophoraceae 



of the United States. (Memoirs of the Torrey Botanica! 



Club. XI. p. 135—250. pl. 20—42. 20. Oktober 1902.) 



Twenty-seven species and two forms are described, with 



critical notes for the Ulothricaceae and twenty-nine species and 



two varieties for the Chaetophoraceae. Some nine species and 



two varieties are recorded as new to the United States and 



numerous forms previously reported by Wolle and others are 



relegated to the doubtful list. Stichococcus is considered as 



deserving generic rank among the Ulothricaceae and Mlcro- 



thamnion is shown to have its affinities with the Chaeto- 



