204 ALGJS 



Schwendener — Monber. Preuss. Akad. Wiss., 1880, p. 327. 



Berthold — Pringsheim's Jahrb. wiss. Bot., 1882, p. 569. 



Schmitz — Sitzber. Akad. Wiss. Berlin, 1883, p. 215. 



Ardissone — Phycol. mediterranea, Part i., Floridete, 1883. 



Buff ham — Journ. Quek. Micr. Club, 1884, p. 337. 



Massee — ^Journ. Microsc. Soc, 1884, pp. l^Z et seq. ; and 1886, p. 561. 



Wille— (Tissue-systems) Bot. Salsk. Stockholm (see Bot. Centralblalt, xxi., 1885, 



pp. 282, 315; xxiii., 1885, p. 330; and xxvi., 1886, p. 86) ; and Nov. Act. 



Leopold-Carol. Akad., Hi., 1888, p. 51. 

 Schiitt— (Phyco-erythrin) Ber. Deutsch. Bot. Gesell., 1888, p. 36. 



A complete classification of the very numerous types of structure 

 belonging to the Florideae would carry us beyond our present limits ; 

 and the principles of such a classification are by no means agreed on 

 by the best authorities, many details connected with the process of 

 fertilisation being still obscure. Agardh, in his ' Epicrisis,' divides the 

 family into six groups, dependent on the structure and mode of develop- 

 ment of the cystocarp, and into twenty-two orders. We shall therefore 

 confine ourselves to an account of some groups or special forms, the 

 structure of which has been specially studied, commencing with the most 

 highly differentiated orders. 



In the CeramiacExB, which are exclusively marine, are included a 

 considerable number of the more delicate red seaweeds of our own and 

 other coasts, included in the genera Callithamnion (Lyng.), Griffithsia 

 (Ag.), Ptilota (Ag.), Crouania (Ag.), Ceramium (Lyng.), and others. The 

 thallus is either monosiphonous and uncorticated, or more or less corti- 

 cated. In Crouania (fig. 1 7 2) the branches are beautifully whorled. The 

 procarp frequently consists of a carpogone and two trichogynes. The 

 cystocarps are formed externally on the branches or at their base, and are 

 frequently closely surrounded by them as by an envelope. With rare ex- 

 ceptions the cystocarp consists of a roundish or lobed nucleus, enclosed 

 in a colourless gelatinous membrane, without any pericarp, and composed 

 of a larger or smaller number of closely packed carpospores. The tetra- 

 sporanges are usually external, and the mode of division of their contents 

 varies greatly. The complicated process of fertilisation in Dudresnaya 

 has already been described. In addition to the tetraspores, two other 

 special kinds of non-sexual organs of propagation occur in the order. 

 Some species of Ceramium are characterised by the presence oifavella, 

 dense agglomerations of spores, resembhng the cystocarps, but pro- 

 duced at the ends of branches, quite exposed except for a thin colourless 

 membrane. They appear to be homologous to the multipartite tetra- 

 sporanges. Callithamnion seirospermum (Griff.) (Seirospora Griffithsiana, 

 Harv.), C. versicolor (Drap.), and some other species, produce seirospores, 



