454 BULLETIN OF THE BUREAU OF FISHERIES. 



Family DICTYOTACEdE (Lamouroux) Zanardini. 



Characters of the order. 



About 1 20 species, all marine, mostly in warm seas, one species extending to 

 Scandinavia. 



KEY TO GENERA. 



a. Frond growing by means of single initial cells situated at the apices 5. Dictyota (p. 460). 



00. Frond growing by means of a group or groups of marginal cells situated at the apices b. 



b. Frond zonate by concentric lines of growth, in the neighborhood of which the spor- 

 angia and gametangia are developed ; fan shaped c. 



c. Hairs lacking on the sterile portions of the frond i. Zonaria (p. 454). 



cc. Hairs present on the sterile portions of the frond 2 . Padina (p. 455). 



bb. Frond uniform, concentric lines of growth lacking; repeatedly dichotomous d. 



d. Midrib lacking - 3. Spatoglossum (p. 458). 



dd. Midrib present 4. Dictyopteris (p. 459). 



Genus i. Zonaria Agardh. 



Zonaria, Agardh, i8 I7 , . XX (in part). 



Frond flat, fan shaped, often ascending from a prostrate lower 'part, growing by 

 groups of cells along the apical margins, forming rather vague, scattered zones, divided 

 into more or less narrow segments, often narrowed at the base of the frond and of the 

 separate segments to a subcylindrical, stemlike portion densely covered by short, brown, 

 rhizoidal filament?, this stemlike structure often continued as midribs for short distances 

 on the flattened segments of the lamina; cortex composed of a single layer of cells 

 arranged in pairs forming longitudinal lines radiating like a fan, each row of paired 

 cells corresponding to a single row of interior cells; inner stratum consisting of several 

 layers of cells; sporangia pear shaped, borne in more or less prominent sori, forming 

 scattered, spotlike patches on one or both surfaces of the thallus, covered by the cuticle 

 as an indusium which is burst as the sorus is elevated and soon disappears, sporangia 

 often surrounded by numerous club-shaped, segmented paraphyses, bearing 8 spores; 

 sexual reproduction unknown. 



About 15 species in warm and tropical seas. 



KEY TO SPECIES. 



Frond entire or nearly so, stipe usually 3 to 5 mm. long i. Z. -variegata (p. 454). 



Frond much divided, stipe usually i to 5 cm. long 2. Z. flaw (p. 455). 



1. Zonaria variegata (Lamouroux) Mertens. PI. XCI, fig. 2. 



Dictyota variegata, Lamouroux, 1813, pi. 5. f. 7. 



Zonaria variegata, Mertens, in Martins, 1828, p. 6, pi. 2, f. a. 



Gymnosorus -oa.riega.lus, De Toni, 1895, p. 227. 



P. B.-A. Nos. 778 (Gymnosorus variegatus.), 2028. 



Frond flat, fan shaped, rather erect on a short stipe, 3 to 9 cm. tall, 4.5 to 14 cm. wide, stipe 3 to 15 

 mm. (usually 3 to 5 mm.) long, thallus entire or more or less lobate, marked by variegated markings 

 radiating from the base and by more or less conspicuous, distant, concentric zonations parallel with the 

 apical margin; sori elliptical, forming broken lines or scattered spots between the zonations; texture 

 thin membranaceous or parchmentlike ; color olive brown to dark reddish brown. 



Florida and West Indies to Brazil; Barbados; Bermuda; Canary Islands; Australian region; Red 

 Sea; Hawaii; Philippines. __ 



Bogue Beach, Beaufort, N. C., one specimen April, 1908, two specimens February, 1909, all sterile. 



In this species the concentric zonations are sometimes fairly conspicuous, sometimes invisible to 

 the naked eye. It is easily distinguished from the following species by its smaller size, shorter stipe, 



