1925] S etch ell-Gardner: Melanophyceae 543 



not been investigated. When first visible, they are very small and it 

 seems likely that they originate through the death, or quiescence, of a 

 cell or small group of cells in the midst of a rapidly growing area, as 

 is the case in some other perforated algae. 



Hydroclathrus clathratus (Bory) Howe 



Fronds very irregular in form, in age much lacerated, 5-16 cm. 

 diam., sessile, attached to the substratum by a broad base, sometimes 

 several bases confluent, differentiated into two layers of cells ; the 

 apertures varying much in size and form and the frond involute along 

 their margins ; color 3'ellowish brown ; hairs in small tufts in the center 

 of expanded sori. 



Growing in tide pools in the lower littoral belt. On the west coast 

 of Mexico near the mouth of the Gulf of California. 



Howe, in Britton and Millspaugh, Bah. Flor., 1920, p. 590; Setchell 

 and Gardner, Mar. Alg. Gulf of Calif., 1924, p. 727. Hydradathrus 

 cancellatus Bory, m Diet, class., vol. 8, 1825, p. 419 ; Harvey, Phyc. 

 Austral., 1859, Tab. 98 ; Mitchell, in Murray, Phyc. Mem., part 2, 1893, 

 pp. 53-56, pi. 15, figs. 2-4. Encaelium ciathratum (Bory) Agardh, 

 Sp. Alg., vol. 1, part 2, 1822, p. 412. Fucus clathratus Bory, MS., 

 fide Agardh, loc. cit. 



The single species of Hydroclathrus is tropical and widespread in 

 both the Atlantic and the Pacific oceans. Our specimens, from the 

 Gulf of California, are old and we have been unable to detect any 

 gametangia. 



FAMILY 11. ^GIRACEAE FAM. NOV. 



Fronds erect, more or less branched, from slightly to decidedly 

 gelatinous ; main growth in length trichothallic, with central axes 

 monopodial and cortical axes sympodial, of two or three tissues, (1) 

 medullary of larger and longer colorless longitudinal filaments, easily 

 separable or compact, (2) intermediate of broad but short colorless 

 cells, and (3) cortical of longer or shorter distinct anticlinal filaments, 

 often curved and enlarged upwards ; both unilocular zoosporangia and 

 plurilocular gametangia known (in some species at least) and borne 

 on similar (macroscopic) plants. 



The family which we have felt constrained to designate as ^gira- 

 ceae is to be separated both from the Chordariaceae (in the narrower 

 sense of Chordaria as limited by the type C. flagelliformis) and from 



