A SYSTEMATIC AND STRUCTURAL ACCOUNT OF AVRAINVILLE A . 99 



coloration of the tips of many of the filaments in A. paimana, 

 mentioned above, is probably due to a larger formation or a 

 modification of this colouring matter. We have been unable to 

 determine the chemical nature of this substance. It is insoluble 

 in water, alcohol, and ether, and is therefore not of the nature of 

 phycophaein or phycoxanthin, neither does it give the chlororufin 

 reaction. In A. longicauUs there are dense brownish masses, similar 

 to those of A. jjajmana; they are sometimes terminal, sometimes 

 intercalary in position. In A. lacerata there is very little colouring 

 matter in most of the filaments, hence the chlorophyll-grains are 

 only slightly obscured, and this species appears much greener than 

 the others, in the dry state. In the living state the fronds of all 

 the species are greener than when dried, having more of an olive- 

 green colour. The change due to drying probably is partly owing 

 to the fading of the chlorophyll, and partly to the darkening of the 

 colom-ing matter, which, however, is present in living specimens of 

 some of the species at^any rate. 



The frond, stalk, and mass of rhizoids of Avrainvillea, except in 

 the case of A. comosa, and very young specimens of A. j^cipuana and 

 others, are composed, as has been said, of much interwoven filaments. 

 The frond is always more or less flabelliform (figs. 1 & 8), and, except 

 in the cases just mentioned, more or less felt-like in texture. This 

 felt-like consistence is perhaps most marked in the frond of A. longi- 

 cauUs (fig. 1), which is at the same time the thickest one of all. The 

 branching of the filaments is, as has also been said, dichotomous in 

 the frond, at all events, though less regular in the rhizoids— and 

 this branching, being for the most part in the same plane in the 

 frond, produces the flabelliform shape. In the stalks the filaments 

 are rather more densely interwoven, and in the rhizoids of all the 

 species and the rhizome-like structure of A. longicauUs a vast 

 amount of coral-sand, small shells, and a multitude of small 

 marine organisms get entangled. The rhizoid mass of A. papuana, 

 when drawn forth, presents the appearance of a cylindrical mass of 

 crumbling mortar, from the great amount of calcareous matter so 

 enclosed. In the other species the corresponding parts are more 

 spongy, and the substance enclosed is more finely-divided detritus, 

 &c. In very young specimens, such as those of A. papuana (fig. 7) 

 from Ceylon (Ferguson) and Borneo (Kjellman), there is little or no 

 interweaving of the frond-filaments, and this is the case with A. 

 comosa in the mature state, though the rhizoids of the last- 

 mentioned species are interwoven in the characteristic fashion. 



We do not cite here specially the case of A. ccespitosa, since we 

 have only the immature specimens to judge by — these are very little 

 interwoven, if at all. The binding together, then, of the frond, 

 stalk, and rhizoids is effected solely by the interweaving of the 

 component filaments. In the neighbouring genera, Penicillus and 

 Udotea, other means are employed for this purpose. The incrusta- 

 tion of carbonate of lime in Penicillus very effectually attains this 

 end ; and Udotea, in addition to an incrustation (sHghter than in 

 the case of most species of Penicillus), is further provided with 

 lateral tenacular filaments. In Udotea such means of cohesion are 



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