Ser. MELANOSPERMEiE. Fam. Bictyotacem. 



Plate XCVIII. 



HYDROCLATHRUS CANCELLATUS, Bory. 



Gen. Char. Frond membranaceous, bag-shaped, hollow, pierced with 

 roundish holes, which dilate more and more, until the plant becomes 

 a clathrate network. Margin of the apertures involute. " Spores 

 minute, globose, collected into dot-like, scattered, innate sori, ac- 

 companied by club-shaped paranemata," Mont. — IIydroclathrus 

 {Bory), corruptly formed from, vBcop, water, and clathrus, a lattice. 



Frons membranacea, saccata, cava, foraminihm pertusa, denium reticulato-cla- 

 thrata; margo foraminum involuius. Sori punctiformes, spar si. 



Hydroclathrus cancellatns, Bory. 



Hydkoclathuus cancellatus, Bory, Diet. Class. Hist. Nat. v. 8. p. 419, 

 Mo7it. Al(j. Alger, p. 36 ; Canar. Crypt, p. 144 ; and Voy. Pol. Sud, p. 

 42. Buby, Bot. Gall. p. 960. Bene. PI. Arab. p. 138. Harv. Ner. Bor. 

 Amer. part \. p. 120. t. 9 A (the young plant) . 



Halodictyon cancellatum, Kiitz. Phyc. Gen. p. 336. 



AsPEUococcus clathratus, /. Ag. Sp. Alg. v. l.p. 75. 



AsPEROcoccus cancellatus, Endl. Sond. PI. Preiss. v. 2. p. 156. 



Encoelium clathratum, Ag. Sp. Alg. v. l.p. 412. Kiitz. Sp. Alg. p. 552. 



Hab. Common near Fremantle, Western Australia, Preiss, Backhouse, 

 W. H. H., G. Clifton, etc. 



Geogr. Distr. Common throughout the tropical and subtropical regions of 

 both hemispheres. Eed Sea. On the shores of Bretagne, Bory. 



Descr. Fronds of very irregular form, oblong or sinuous, from 2-6 inches long 

 or more, heaped together in widely spreading patches, and adhering to 

 rocks by their lower surface,, and to one another by their sides. The 

 young fronds, from a very early age, are pierced with round holes. At first 

 these holes are of small size, and often laterally compressed, but as the 

 membrane expands, the holes widen, and in the full-grown plant (repre- 

 sented in our Plate) the apertures frequently are one or more inches in dia- 

 meter and of irregular shape ; new holes open in the interspaces, and the 

 frond is converted into a delicate, bag-shaped network. The margin of 

 each hole is strongly involute. The substance is thickish, crisp when quite 

 recent, and in that state very fragile ; but on exposure to the air it soon 

 softens. The young fronds decompose rapidly in the air or in fresli-water, 

 but the full-grown are more tenacious, and t!ie old become even rigid. The 

 colour when young is a very pale yellowish-olive ; afterwards it grows darker, 

 and in age is a rusty-brown. In drying it rarely (except when young) 

 adheres to paper. I have not seen the fructification; 



