MATERIAL EXAMINED 13 



M. V. Lebour. The order of the genera given in the tables of analyses is that adopted by 

 the last-named in her works on the Dinoflagellates (1925) and the Planktonic Diatoms 

 (1930) of northern seas. The species have been arranged alphabetically. 



It should be obvious that work of the nature here described can only be accomplished 

 with the co-operation of a large number of people. The entire scientific staff has been 

 engaged at some time or another in the collection of the material at sea, and this is only 

 rendered possible in the first place by the able co-operation of the marine staff. In 

 addition useful ideas have often accrued from discussion with the other members of the 

 scientific staff, which are acknowledged in the appropriate sections of the paper. 

 Prof. A. C. Hardy, sometime second scientific officer of the Expedition, has given the 

 benefit of his experienced advice, and I am also indebted to Dr W. H. Pearsall, of 

 Leeds, and Mr H. W. Harvey, of Plymouth, for their opinions on some points. Thanks 

 are due to Mr F. W. Mills for checking the references to the diatom species, to Miss 

 E. C. Humphreys for preparing the figures for reproduction, and to the authorities of 

 the British Museum (Natural History) for laboratory and hbrary facilities. 



MATERIAL 



The material upon which this paper is based consists of a large number of vertical 

 hauls of the Gran half-metre net, fished usually from 100 m. to the surface. At the 

 majority of the stations full hydrological observations were taken. At a very few stations 

 centrifuged water samples were also examined. 



It will be seen that the material is considered in five sections, partly for the sake of 

 convenience ; but the division is also more or less a natural one. 



The collections round South Georgia include two surveys made by the R.R.S. 

 'Discovery H' in January-February 1930 and in November 1930. In addition a line 

 of stations worked to the north of the island later in the season 1930-1 by the R.R.S. 

 ' William Scoresby ' is dealt with, and the main evidence supported by the examination 

 of material from isolated stations worked by both ships on arrival and departure from 

 the island. 



Seven lines of stations crossing the Antarctic convergence are examined in the section 

 dealing with the transition from Antarctic to sub-Antarctic phytoplankton. These were 

 taken at times of year varying from November to April. All cross the convergence to the 

 west of South Georgia, some being worked on passage from the Falkland Islands, others 

 across Drake Passage from the South Shetlands to Cape Horn, and the rest crossing the 

 convergence at various points between these two extremes. Of these lines four were 

 made by the R.R.S. 'Discovery H' and two by the R.R.S. 'William Scoresby', while 

 on one both ships were employed. 



The section dealing with the phytoplankton of the Weddell Sea area is based mainly 

 on the season's work in 1930-1. A few stations worked by the R.R.S. ' Discovery II ' in 

 the neighbourhood of the South Sandwich Islands in February-March 1930 are, how- 

 ever, included. During the following season, a large amount of material was collected 



