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concentric striations, in older ones rather uneven, bullate and often 
somewhat folded. The thallus is rather easily separated from thè sub- 
stratum. 
Fig. 1 . Ralfsia expansa J. Ag. a. transverse section of thè thallus with uni 
locular sporangia b. transverse section of thè thallus near thè edge (40 : 1). 
The sterile part ot thè thallus is built in good accordance with 
that ot Ralfsia verrucosa : from a horizontal layer of cells, archfor- 
med cellthreads grow up turning their convex side against thè edge 
af thè thallus, agreeing with Reinke’s schematic figure of Ralfsia 
verrucosa in a Algenflora » p. 48 ; often thè leaf is more or less bi- 
lateral as shown in fig. 1 a and b being li ke thè figure c ot Reinke 
1 . c. referring to some form from thè Channel of Ralf sìa verrucosa. 
The chromatophore in thè material preserved in alcohol was 
not especially prominent; it was plateformed and a single one was 
found in each celi. Groups of hairs occur rather abundantly. 
Both unilocular and plurilocular sporangia were met with, oc- 
curring on different plants. The unilocular sporangia (fig. 2 a and b) 
are laterally placed upon thè paraphyses and nearly always stalked, 
having a single basai celi, very seldom I have found sporangia without 
this celi. 
They are oblong - pyriform but as to thè form and size some 
differences occur. In one specimen from thè reef between thè Hurn- 
cane lsland at St. Thomas they were nearly ovai - pyriform, 75 (x. 
long and 3o ji. broad and thè paraphyses about 100 long; (fig. 2 a), 
in another specimen collected at thè French wharf in thè haibour 
