104 



we find two specimens in Lamoi roux's herbarium. One is A. stelligera Lamk.; the other is identical 

 with . /. similis Sond. The first specimen has "bourrelets aux deux extrémités" as Lamouroux called 

 the swelling at the top and at the base of the joints in his A. verrucosa, swellings which however 

 are not always to be found there and often disappear in old age. On account of these "bourrelets", 

 I think that A. verrucosa ma) be taken as a synonym of M, stelligerum. A. stellulata, which 

 Aki as a synonym of A. charoides, I believe to belong to M. graniferum. 



M. stelligerum is like the two other species an inhabitant of Australian seas. 



Litharthron n. g. 



PI. XVI, fia. 16, 17. 



The alga known as Amphiroa australis belongs, different as its anatomical structure may 

 be, to the Corallineae. This difference was first observed by Kützixg, to whose sharp eyes 

 little indeed escaped that concerned algae. He was so much struck by the aberrant structure 

 of Amphiroa australis, that he expressed his doubts as to whether it could be kept amongst 

 the Amphiroae. 



Mv studies have taught me, that Amphiroa australis, for which I propose the name 

 Litharthron australis, must be kept in the family of the Corallineae and that its place is — 

 different as their outward appearance ma} - be, — close to Metagoniolithon stelligerum. Some of the 

 characters which distinguish this latter plant, only still further cleveloped, are also the characters 

 of Litharthron. The cells of the central strand in the joint are non-calcified, just as in old plants 

 of M. stelligerum, but in L. australis these cells are intricated and imbedded in a mucilaginous 

 layer. The cells of the cortical layer of L. australis are big, calcified, thin-walled, filled with 

 starch near the central strand and becoming gradually smaller towards the periphery; in M. 

 stelligerum the primary cortical layer of calcified cells is thrown off; the secondary cortical layer 

 has round, big cells growing smaller towards the periphery but they are non-calcified and thick- 

 walled. I do not know the nature of the mucilaginous layer in which the central strand ot 

 Litharthron is imbedded but after putting thin sections of this plant on a slide with a drop 

 of sea-water, I saw the central part of the section swell up. With the polariser numerous 

 brilliant spots were visible to the right and left of this central layer, which itself remained quite 

 dark under the crossed nicols. But it was not the whole central strand that was non-calcifiecl ; 

 at its periphery I saw distinctly long cells imbedded in a layer that contained chalk. 



In the node the cells were of different size, and presented the aspect of an ordinary 



Florideae-tissue ; here also a distinct cortical layer was visible. From the node spring the branches 



as in the different species of Metagoniolithon. The flatness of the node is a character of small 



mportance, but it is a great help towards recognizing L. australis at once amongst a collection 



Corallineae. I fancy however that in a living state the flatness of the joint would be less 



remarkeable, owing to the mucilaginous layer in the middle of the joint being then swollen. 



The conceptacles have not vet been found: I can only hope that they may soon be 

 overed ai ui that they will coniirm my views about the genus Litharthron. 



rthron, just like Metagoniolithon is an inhabitant of the Australian seas. It has 



