SPH^ROCOCCOIDEJi;. 139 



Some of the forms of this plant resemble D. Hypo- 

 glossum so closely, that the difference is scarcely per- 

 ceptible to the naked eye ; but when the two plants are 

 examined under the microscope, the distinctive characters 

 which separate them are very easily perceived. In D. ■ 

 ruscifolia the membrane is composed of very minute, 

 closely-packed cellules, and the veinlets are very dis- 

 tinct, while in D. Hypoglossum the cellules are compara- 

 tively large and wide apart, and either there are no 

 veinletSj or they are very faint. This species is annual, 

 and to be found from spring to the end of autumn. 



Genus LII. NITOPHYLLUM. 

 Frond rose-red, membranaceous, irregularly cleft, Mitbout 

 a midrib, either veinless or with a few slender, branched, 

 vanishing veins near the base. Spores elliptical or roundish, 

 in globose, stalkless conceptacles scattered over the surface 

 of the frond ; tetraspores grouped in spots, or sori, also 

 scattered over the frond. — Nitophtilum, from the Latin 

 niteo, to shine, and the Greek phyllon, a leaf. 



This genus has many characters in common with 

 Delesseria,^e principal difference between them beingthe 

 form of the frond, which is irregular and unsymmetrical 

 in Nitophyllum, and regular and leaf-like in Delesseria. 

 All the species of the latter genus, moreover, have dis- 

 tinct midribs, while in those of the former, that organ 

 is only represented by very slender, often vanishing 

 veins, which are altogether absent in some species. All 

 the species are annual, and flourish during summer and 

 autumn. As a rule they grow in deep water, and can 

 only be observed in situ during extreme low-tides. They 

 are, however, constantly thrown on shore, either on the 

 stems of Laminarice or detached. 



