936 REPORT— 1900. 



(2) Assimilation Experiments. — A frond of tlie sea-weed was placed in various 

 mixtures in succession (a) of polluted sea-water, (b) polluted sea-water plus 

 sewage, (c) polluted sea-water with sewage and ammonium salt, (d) sea-water 

 plus nitrates. By determinations of free and albuminoid ammonia, and nitrates in 

 these mixtures hefore and after the sea- weed had been in contact with them, the 

 power of assimilating nitrogen which the weed possesses was ascertained and was 

 found to be remarkably high. Thus in one experiment it absorbed the whole of 

 the free ammonia from a polluted sea-water containing O'OSO part per lOO'OOO in 

 seventeen hours. Nitrates were also rapidly absorbed, but not albuminoid 

 matters. The weed remained in perfect health during these experiments and is 

 still growing, although nine months have elapsed since the experiments were 

 commenced. 



(.3) The Localities ivhere Ulva latissima abounds, and from which it is 

 virtually absent. — As stated above the sea-weed is present in abundance in Belfast 

 Lough, but it is almost entirely absent from Strangford Lough, which is similar 

 in area and in many other respects to Belfast Lough, but differs from it in not 

 being extensively polluted by sewage. In Dublin Bay the sea-weed is found in 

 quantity in the harbour, which is highly polluted, but not in the southern parts of 

 the bay, which receive no sewage — except near Kingstown, where a large sewage 

 tank discharges on the ebb tide. There the weed occurs. 



The evidence which the authors have collected tends tlierefore to the conclu- 

 sion that the occurrence of Viva latissima in quantity in a given locality is an 

 indication of sewage contamination, and there can be no doubt as to the power 

 which the weed possesses of absorbing nitrogen compounds from polluted sea- 

 water. AVbile thus acting as scavenger it may itself give rise to a very extensive 

 nuisance. 



6. Germination of the Zoospore in Laminai'iacece. 

 By J, Lloyd Williams. 



The zoospore comes to rest and assumes a spherical form. The single chloroplast 

 divides in two. A tube is produced and the contents pass into it. At the end of the 

 tube a swelling is formed, into which all the contents migrate, and are shut off from 

 f the empty spore-case and tube by a wall. This has been wrongly regarded by 

 ll, I Areachong, in \he c&se of Dicti;osiphon, as a case of sexual fusion. In the en- 

 largement the chloroplasts multiply and additional eye-spots appear on several, 

 which, however, disappear after a few days. The newly separated cell now 

 divides and forms a branched protonema-like structure. %-o\. b.^^q 



7. Professor Percy Groom delivered a Lecture on Plant-form in 

 Relation to Nutrition. 



SATURDAY, SEPTEMBER 8. 

 The following Papers were read :— 



L On Double Fertilisation in a Dicotyledon — Caltha palustris.' 

 By Ethel N. Thomas. 



This research was undertaken at Miss Sargant's suggestion, because of tbe 

 extreme importance of the discovery of double fertilisation in Monocotyledons 

 by Professor Nawascbin and later by Professor Guignard. 



The work was carried out at the Royal College of Science, South Kensington, 

 and among other plants Professor Farmer recommended Caltha palustris. 



' Published in Annals of Botany, vol. siv., September 1900. 



