Order 10. =Delesseriaceæ.= _Delesseria sanguinea_; _D. alata_ and _D. sinuosa_ are handsome forms which are not uncommon. Order 11. =Bonnemaisoniaceæ.= _Bonnemaisonia._ Order 12. =Rhodomelaceæ.= _Rhodomela_, _Odonthalia_; _Polysiphonia_, of which many species are to be found on the coasts of Great Britain, has a filamentous, richly branched thallus consisting of a central row of cells surrounded by a varying number of cortical cells of similar size--the so-called “siphons.” Order 13. =Ceramiaceæ.= Pretty Algæ, often branched dichotomously, or unilaterally pinnate. _Spermothamnion, Griffithsia, Callithamnion, Ceramium, Ptilota._ Sub-Family 4. =Cryptonemiales.= The cells formed by the coalescence of the auxiliary cells and the ooblastema-filaments, produce the gonimoblasts. The _carpogonium-filaments_ and the auxiliary cells are scattered singly in the thallus. Order 14. =Gloiosiphoniaceæ.= _Gloiopeltis._ Order 15. =Grateloupiaceæ.= _Halymenia, Cryptonemia._ Order 16. =Dumontiaceæ.= _Dumontia, Dudresnaya._ Order 17. =Nemastomaceæ.= _Furcellaria_, which has dichotomously branched, round shoots, is common on the coasts of Great Britain. Order 18. =Rhizophyllidaceæ.= _Polyides, Rhizophyllis._ Order 19. =Squamariaceæ.= The Algæ belonging to this order form crust-like coverings on stones, mussel-shells, and on other Algæ, but are not themselves incrustated: _Petrocelis_, _Cruoria_, _Peyssonellia_. Order 20. =Corallinaceæ.= Partly crustaceous, partly erect, branched Algæ, thickly incrusted with lime, so that a few species (_Lithothamnia_, also called _Nullipora_) occur in fossilized condition from Jurassic to Tertiary periods. _Melobesia, Lithophyllum, Lithothamnion, Corallina._ USES. “Carragen” is the thallus of _Chondrus crispus_ (Irish Moss) and _Gigartina mamillosa_. It is a common article of food on the coasts of Ireland, and swells to a jelly when cooked. It is officinal. _Rhodymenia palmata_ is generally eaten as food in Ireland and in some places on the west coast of Norway; it is also used as food for sheep and hence is termed “Sheep-seaweed.” Agar-Agar is the jelly obtained from species of _Gelidium_ and _Gigartina_ growing in China and Japan. Sub-Division III. =FUNGI.=