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Part III. — Fifteenth Annual Report 



V.— REPORT OF OBSERVATIONS ON PLANT PLANKTON. By 

 George Murray, F.R.S.E., F.L.S., Keeper of the Department of 

 Botany, British Museum. 



At the request of the Board I have carried out a series of observations 

 on the minute free-floating vegetation, especially of the west coast. The 

 importance of a study of such organisms, as the basis of the nutrition of 

 all life in the sea, has long been recognised, but very little has hitherto 

 been done in the way of investigation. The main observations were 

 made on board the ' Garland ' in three series, viz., the first from 26th March 

 to 6th April ; the second from 28th July to 15th August; and the third 

 from 2nd December to 8th December. In March to April, the observations 

 were made in the North Sea, and on the west coast in Loch Linnhe, the 

 Sound of Jura, and principally in the Clyde sea-area. In July to August 

 a week was spent in visiting the former stations and others in the Clyde 

 sea-area, and the remaining time in the Sound of Islay, Sound of Jura, 

 Firth of Lorn, Loch Etive, Loch Linnhe, Loch Aber, Sound of Mull, the 

 sea round Rum, Eigg, and Ardnamurchan, Loch Nevis, Loch Hourn, 

 Raasay Sound, etc. In December, observations were made in Loch Aber, 

 Loch Linnhe, Firth of Lorn, and the Clyde sea-area. The material ob- 

 tained at these times was all preserved, and its working out in detail 

 occupied me for a considerable period in London. 



Methods. — In addition to tow-netting with fine silk nets — the method 

 of capture usually employed — I have made use of a cylindrical silk bag, 

 about 1J feet long and 3 or 4 inches wide. This was tied to the nozzle 

 of the hose, there being a lateral overflow vent near the top of the bag ; 

 and, on pumping through it with the donkey engine from an intake pipe 

 8 feet below the surface, good results were obtained. This method, first 

 employed by Dr John Murray, enables one to work when steaming, and 

 is often convenient in weather that is too rough for tow-netting. The 

 fixing and preservative employed was a 0'5 per cent, aqueous solution of 

 chromic acid ; good results have also been obtained from Fleming's solution 

 and from platinic chloride of various strengths. I carried tubes half filled 

 with the chromic acid solution, which is about the same density as 

 ordinary sea- water. The diatoms, etc., were turned out of the tow-net into 

 a glass-jar, and allowed to settle for some time. They were then collected 

 from the bottom by means of a dipping-tube, and added to the chromic 

 acid solution. Several times during summer, while working in haste and 

 having large quantities of diatoms to deal with, I removed some en masse 

 with a spoon from the tail of the net to the chromic acid solution. The 

 addition of a mass of diatoms, without the proper proportion of sea- water, 

 proved to be a mistake, since the contents of the cells were disorganised 

 in these cases. 



Distribution. — The seasonal occurrence of diatoms in vast numbers 

 in the sea has long been known, but no observations have been made that 

 afford a satisfactory explanation of the causes that contribute to the 

 phenomenon. On both the east and west coast, during the first months 

 of the year, there is a remarkable prevalence of diatom life. We have 

 no knowledge of the distance out in the Atlantic to which this extends, 

 but in the coastal waters at this season the abundance of diatoms is extra- 

 ordinary. Towards the end of March and beginning of April, the quantity 

 diminishes, and for the rest of the year diatoms remain at a fairly con- 

 stant quantity, except for here and there the occurrence of definite local 



