in oreat quantities in all Lithothamnia of the tropical seas. And not only Lithothamnia but also 

 corals have to suffer from these algae. Duerden *) writing about algae as coral disintegrating 

 agents says p. 326: "the surface of many corals, even when covered with the polypal tissue is 

 strongly green in colour .... (due) to the presence of green filamentous algae". 



Wonderful is Hfe <>n a coral reet and the various agents now building up and then 

 destroying again whal scarcely was developed, wil! ever afford a tempting object of study 

 t<. Naturalists. 



In the above quoted paper on the Lithothamnia of the Laccadive and Maldive Islands 

 Fosi ie observes that "the Lithothamnia of the Tropics have been rather disregarded". In latter 

 years, thanks to several collections that were sent for investigation either t<> Foslie or to 

 Heydrich our knowledge of these plants bas much increased and the collections of the Siboga, 

 to which were added some specimens brought home by the Dutch New-Guinea Expeclition, 

 will help to <^ïve us a fairly good idea of the distribution of Lithothamnia in the Indian Seas. 

 [E has described in the following pages 32 species of Lithothamnion and other genera, 

 belon^iiiL; to the group of the Melobesieae Aresch. •. amongst these seven are new to science, 

 and three, which I "had studied while still on board H. M. Siboga, were published shortly after 

 my return, in our joint names, and here I should like to say, how happy I am to have secured 

 for the collections of the Siboga the valuable collaboration of Mr. Foslie. His extensive 

 knowledge of all existing Lithothamnia gives us hope, that he will bring order into this most 

 confusing group. 



It was first understood between us, that Mr. Foslie should work out the incrustine and I 

 the branchingf Lithothamnia. but I soon discovered that I should be most grrateful if he would 

 undertake the namins: of them all. The Corallineae verae. of which the Siboga material contained 

 several genera and species were to be worked out by me alone and the paper in which both 

 groups Melobesieae Aresch. and Corellineae verae were treated, appear under our joint names. 



The Corallineae verae: Amphiroa^ Cheilosporum, Jania and Corallina, slender plants 

 as thev may be, are very active reef-builders, indeed, taking their smallness into account, it is 

 astonishing to observe how much sand may be kept together by their tiny branches. They 

 illustrate often in a wonderful manner how true the words of Walther are: "Das Wesen der 

 Riffbildung beruht im Sandfansren". 



Corallineae verae were gathered by the Siboga to a clepth of 36 m. On the Borneo 

 bank beautiful, long-creeping specimens of Cheilosporum spectabile Harv. were found. Large 

 squarrose Amphiroae were abundant along the south-east coast of Timor, indeed almost every 

 reef yielded one or another species of this genus. Still I could not detect more than a single, 

 new species among my collection. The French investigators who explored the eastern part ot 

 the Archipelago during the beginning of the nineteenth century had already gathered them all, 

 and they wen; described by Lamouroux. 



I would like to express here my sincere thanks to Prof. Lignier of Caen for lending 

 me so liberally the Amphiroae out of Lamouroux's Herbarium. 



EN. Al 1 . a\ disintegrating Agents. Buil. Amer. Mus. of Nat. Hist. 1902. XVI. 



