114 DICTYOTACE^.— PmcTAEiA. iv. 



of many rows of elongated cells, disposed longitudinally and firmly united into a 

 compact cellular substance. The innermost of these are very long, the outer pro- 

 portionably shorter. All, except those that compose the outermost row or circle, 

 are colourless, and nearly empty. 



1. DiarrosJF'Eas fcmiculaceus,Gvey. ; frond setaceous, very much branched ; the 

 branches capillary, decompound ; ramuli subulate, alternate or scattered, rarely 

 opposite. — /. Ag. Sp. Alg. vol. l,p. 82. Kictz. Sp. Alg. p. 485. Harv. Phyc. Brit, 

 t. 326. 



Hab. In rock pools, between tide-marks on stones and the smaller Algas. Sea 

 shores from New Brunswick to Long Island Sound. Prince Edward's Island, Dr. 

 Jeans. Halifax, W. H. H. Boston Bay, G. B. Emerson and Mrs. Asa Gray, ^c, 

 Rhode Island, Mr. Geo. Hunt., Mr. Olney, ^c. Arctic Coast, Mr. Seeman. (v. v.) 



Fronds from six inches to one or two feet long, about as thick, or sometimes twice 

 as thick, as hog's-bristle, much branched and bushy ; usually having an undivided 

 stem, set with many lateral branches, which are furnished with one or two series of 

 lesser branches, also lateral, and very unequally and irregularly placed. Primary 

 branches as long as the leading stem, or longer, very numerous. The spores are 

 plentifully scattered over the branches, and are usually solitary. Colour a greenish 

 or a brownish olive. Substance membranous, soft, but not gelatinous, adhering to 

 paper in drying. 



yill. PUNCTARIA. Grev. 



Root a small naked disc. Frond flat, ribless, membranaceous, undivided. Fruc- 

 tification, minute, dot-like sori, scattered over the whole surface, and containing 

 roundish, sessile spores., accompanied by a few short, club-shaped, jointed parane- 

 mata. 



The species comprising this group have the leaf-like habit of the smaller Lami- 

 nariaB, such as L. Fascia ; or of the restricted genus Ulva, in which, by the older 

 botanists, they would all have been placed. From Laminarise they differ in being 

 of a more reticulated structure, formed of larger cellules, and in the very different 

 fi-uctification ; and from the Ulvse in colour as well as structure. To the genus 

 Asperococcus, which immediately follows in order, Punctaria is very closely related, 

 and only to be distinguished by the flattened, not tubular frond. But in Asp. 

 compressus we find a strictly intermediate form, nearly as flat as a Punctaria, but 

 evidently composed of two separable membranes. 



