TRANSACTIONS OF SECTION K, 



851 



stage of Physalospora. A third form of fungus — a Diplodina-'Closelj allied 

 to Diplodina salwis, West, was also present. Infection experiments -were also 

 described. 



8. On the Occurrence of Ulva latissima and Enteromorpha compressa in 

 Sewage Effluents, and on Variations in the Composition of the Tissues 

 of these and Allied Seaioeeds. By Professor Letts, D.Sc, Ph.D., and 

 J. S. TOTTON, B.A. 



The view expressed by one of tbe authors in conjunction with another chemist,^ 

 that the growth of Ulva latissima in quantity in a given locality is a sign of 

 sewage pollution, has received remarkable confirmation by the occurrence of the 

 seaweed under very peculiar circumstances. 



About a year ago it was observed that a green growth had made its appearance 

 on the fragments of brick used as the filling material in one of the experimental 

 contact beds (lower series) employed in the purification of the Belfast sewage, and 

 that this growth had the appearance of one of the varieties of green seaweed at an 

 early stage of development. By the spring of the present year the surface of the 

 contact bed had become dotted with patches of Ulva latissima, several of which 

 were a foot or two in diameter, and the fronds of the seaweed four or five inches 

 in length. 



At another part of the works, the sewage after treatment (by septic tank and 

 subsequent double contact with filter beds) was allowed to flow into a shallow 

 lagoon, and there another green seaweed, Enteromorpha compressa, developed in 

 abundance. 



The authors are of the opinion that the spores of these two species of Algm 

 must have found their way into the sewage by leakage of sea water into the 

 system — a view which is strongly supported by the high proportion of chlorine 

 present in the sewage— seventy parts per 100,000 being found as the mean of 

 twelve determinations, whereas ordinary sewage contains only from six to ten 

 parts. 



The occurrence of these seaweeds under the conditions stated above induced 

 the authors to study the chemical composition of their tissues with the view of 

 ascertaining to what extent the latter would be modified by environment or food 

 eupply. 



The following somewhat remarkable results have been obtained with the care- 

 fully washed and dried seaweeds : — 



Ulva latissima — 

 From the sewage contact beds . 

 „ Belfast Lough , 

 „ Lame Lough . . , 



Enteromorplia compressa — 

 Growing in sewage effluent 

 „ „ Lame Lough . 



Enteromorplia iivtestinalis — 



From brackish ponds near Belfast 

 „ Lame Lough . 



The authors desire to express their thanks to Professor Gregg Wilson and to 

 Mr. Thornton for their assistance in identifying and supplying them with some of 

 the specimens employed in the above investigation. 



' Letts and Hawthorne, Proc. Roy. Soc. Edinlnrnh, 1901, p 2G8, and Srit, 

 psoc, Report, 190Q. 



,3ii 



