MAEINE ALGiE OF THE ' SEALAEK ' EXPEDITION. 115 



Seychelles, Long Island. 

 Distribution. Bed Sea ; Indian Ocean. 



Etjcheuma, J. Agardli. 



1. EucHEUMA CoTTONii, n. sp. (Plate 12. fig. 2.) 



Thallo crasso, carnoso, depresso, decumbente, lateraliter et subdicliotomice ramoso, 

 latere superiore verrucis et tubereulis aggregatis, latere inferiore tuberculis remoti- 

 oribus obsito. Verrucis nonnunquam forma irregular!; tuberculis vulgo parvis ct 

 rotundis, nonnunquam apiculatis. Hegione mediaaa thalli ad apices e cellulis satis 



bypbis circumdatis constante, byphis infra item auctis et cellulas satis 



mag 



& 



magnas formantibus; peripberiam versus cellubs diminutis ct ibidem scries b 



formantibus. Organis fructificat 

 Saya de Malba, 25 fms. ; in alcobol 

 Car^ados Carajos, 26 fms. ; dry specim 



E. Cottonii is unfortunately a barren plant, and sbows, in a dry state, a groat li! 



to species of Gracilaria. I moistened it, to restore as much as possible its natural 

 appearance, and was tben struck by its great resemblance to Eucheuma. The figures 

 are made from these moistened specimens, and show well the horizontally spread, 

 laterally branched thallus, covered with warts and more or less pointed tubercles. 

 The anatomical structure at the apex is also entirely different from that of Gracilaria, 

 thou-h, in a cross-section at some distance from the apex, only round, rather large, and 



thick-walled cells are to be seen. But tbese cells are of different origin to 

 the primary large cells, for at the apex the latter are seen to be surrounded by narrow 

 hypbse, which grow out lower down into large cells and are then no longer discermble 



as liyphse. , 



The genns Eucliei^ma is described by Schmitz in Engler u. Prantl, ' Pflanzen-Eamilien, 



as having a central axis of slender elongated hyph^. This axis is found, for mstance, 



onllArl nttfintion to the fact that E. Schrammi 



somew 



in E. S2)inosum. Agardh has, however, called attention to ^ ^ 



has a structure in which " fila strati interioris sparsim inter cellulas strati intermedn 



quasi introducta obveniunt." Schmitz, again, supposes that E Schrammi, Crouan, is 



not an Eucheuma but an Eimjomma. 



My studies on the Enclieumata of the Malay Archipelago seem to indicate that there 

 are species of Eucheuma without a central axis of longitudinal hyphse. The mvesti- 

 gations are not complete, but it appears to me not improbable that the cylindrical erect 

 species have an axis of narrow cells, and that in the flat prostrate species this is absent. 

 I did not find an axis in any prostrate specimens of Eucheuma of which I was able to 

 study the cystocarp. The whole question needs to be further investigated, but for 

 the present it seems highly probable that the alg^ from Saya de iMalha and Cargados 

 Carajos belong to the genus Eucheuma, and the name 1 propose for it is in kind 

 remembrance of Mr. Cotton's friendly help. 



S2 



