84 



marked by Amphiroa ephedraea where the node consists of the whole central strand and the 

 whole cortical layer, and intervening forms between these two extremes are numerous. 



To the treillis Amphiroa belong those plants which have fronds built up of a central 

 strand of filaments having alternating rows of long and short cells communicating with one 

 another by primary and secondary small pores. How these rows of cells alternate is a question 

 of less importance and this will be considered when treating of the different species. The 

 have conceptacula as wartlike protuberances on cylindrical joints {Euamphiroa Dec. 

 pro parte) or as conical processes on flat two-edged joints [Eurytion Dec.) or half immersed 

 in the tissue of the frond: A. crassa, A. triöulus. Their nocles consist always of the central 

 strand ; the cortical layer may split off and leave the node naked, or persist and take part in 

 the formation of the node. The rows of cells of the central strand have with rare exceptions 

 ame size in the node as in the joint. All Amphiroae have a layer of "Deckzellen" covering 

 their growing tops. 



I propose the name of Metagoniolithon for those algae which have joints consisting of 

 rows of cells all of the same dimension and communicating in their longitudinal walls by relatively 

 big thin places in these walls. The whole central strand and cortical layer take part in the 

 formation of the node, the cells of which are much smaller than in the joint. The ramification 

 takes place at the node and from the non-calcified tissue of the node spring forth successively 

 new branches, which are therefore no true whorls, though they surround the node like a whorl. 

 On sectioning the young top of Metagoniolithon graniferwm [Amphiroa granifcra Harv.) I saw 

 that it was covered by a thick mucilaginous layer in which slight striae were visible, reminding 

 me of the Membranprismen, described by Solms-Laubach for Corallina mediterranea. I saw no 

 layer of "Deckzellen". 



Their conceptacles have the form of conical processes. These are flrst seen on the inner 

 side of secondary branches, but in old fronds they are scattered along the whole branch. 



To Metagoniolithon belong the following three species, known as species of Amphiroa : 



Metagoniolithon charoides Lamx. 

 Metagoniolithon granifernm Harv. 

 Metagoniolithon stelligerum Lamk. 

 Lithothrix aspcrgillns Gray {Amphiroa aspergillus Anders.) is such an aberrant alga, 

 that it could not be kept amongst the Amphiroae, by anyone who decalcifies and sections its 

 joints. It will be spoken of in the succeeding pages, as will also Amphiroa aiistralis Sond., 

 which proved to be so totally different that it had to be taken out of the genus Amphiroa. 

 I propose for it the name of Litharthron ; the diagnosis of this genus will be found in the 

 following pages. Neither Metagoniolithon nor Lithothrix nor Litharthron were to be found 

 tiongst the collection of the Siboga; I looked at these different algae for comparison with 

 Siboga-material, and thus found out, that they were generically different from Amphiroa 

 and also from one another. 



genera Arlhroeardia, Cheilosporum, Jania and Corallina are closely allied. In all 



mr the central strand of filaments is built up of cells of equal dimension throughout the whole 



joint. In Arthrocardia and Cheilosporum the cells communicate, both by their primary pores, 



