664 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the heterocyst. A number of spherical gonidia an- formed, each 

 of which is capable of dividing to form a new Anabmna filament. 

 L2. Anabsena Gycadese maintains iis existence in the soil in the form of 

 heterocysts and spines, which develop into gonidia, and these enter the 

 Cycas tubercles through the lenticels. Twenty-six figures illustrate 

 this paper. 



New Species of Nostoc* — L. (iain describes two new species of 

 Nostoc collected on the French Antarctic Expedition (l!)08-lo). The 

 author mentions that he has been aide to identify about twenty different 

 species of algas, mainly Cyanophyceae and Desmidieae, among mosses 

 and in damp places. The first of the two new species is Nostoc Borneti, 

 from Jenny Island, within the polar circle, and is allied to N. ceeruleum 

 Lyngbye, which it resembles in its globular firm habit, its transparent 

 mucilage, its sharp polished outline, dense sinuous trichomes, and 

 indistinct sheaths. But it differs from N. cseruhum in its smaller size. 

 The course of development is described for N. Borneti. The second 

 species is K. pachydermaticum. also found among mosses and other algie 

 at Jenny Island. This belongs to the section Communia Born, and 

 Flah.j in the neighbourhood of N. commune Vauch. 



Ulva latissima.f — A. D. Cotton writes a report on the growth of 

 Ulva latissima in excessive quantity, with special reference to the Ulva- 

 nuisance in Belfast Lough. The report deals with the botanical aspect 

 only, and it is divided into three parts, namely : (1) a description of the 

 growth of Ulva on the Belfast sloblands ; (2) an account of various 

 other localities investigated with a view to explaining the conditions 

 which bring about excessive Ulva-gvowih ; and (3) a general summary 

 of the ecology of Ulva, a discussion on the question of its growth in 

 excessive quantity, and the conclusion as to Belfast. One of the most 

 interesting results obtained by the investigation is the discovery of the 

 important part played by mussels in connexion with an excessive growth 

 of Ulva. He says that these molluscs, like Zostera, can cover ground 

 on which Ulva could find no anchorage, but, unlike Zostera, they afford 

 an excellent mooring for the Ulva. The presence of mussels and an 

 excessive growth of Ulva in estuaries will probably be found to be very 

 intimately connected. Mussels are capable of covering many acres on 

 flat shores which would otherwise be bare mud or fields of Zostera. and 

 the result of the mussel-covering is a growth of Ulva. The principal 

 conclusions are summed up shortly : Of the conditions necessary for the 

 growth of Ulva in the littoral region, two may be singled out as of the 

 very greatest importance : (1) the absence of rough water; and (2) the 

 presence of a substratum which affords a suitable anchorage for the 

 plants. The latter is supplied by the molluscs, as mentioned above. 

 I Ira is proved to be an alga that thrives in pure sea-water, and in 

 polluted brackish water. Being a marine and not a fresh-water organism, 

 its grow tli in polluted estuaries is probably to be regarded as an adapta- 

 tion. In sewage-contaminated water it' absorbs large quantities of 

 ammonia, and its tissues are found to contain a much larger proportion 



* Coraptes Iiendus Acad. Sci. Paris, clii. (1911) pp. 1691-4. 



t Royal Commission of Sewage Disposal, rep. 7, app. iv. (1911) 23 pp. (1 pi.). 



