SEAWEEDS 



SEA-WOLF 



289 



The Dictyotacese are an aberrant group of Phaeo- 

 phycese with distinct affinities to the Rhodophycea>. 

 They resemble that group in having non-motile 

 spores produced in fours in sporangia which 

 are clustered in sori over the surface of the 

 frond (Dictyota) or along the midrib. The 

 exual organs are in the form of antheridia and 

 oogonia. The male organs produce non-motile 

 fertilising cells resembling the pollinoids of the 

 Rhodophycete, though Johnson (Jour. Linn. Soc. 

 Hot., vol. xxvii. p. 467) considers that possibly the 

 pollinoids of Dictyopteris may be ciliated like those 

 of Outleria. The oogonia are arranged in sori, 

 each containing one ovum. In both rucaceie and 

 Dictyotacea- fertilisation is external. 



The Rhodophycese ( Floridese ) form a very large 

 assemblage or most varied vegetative form, and 

 every possible shade of red from a purple black to 

 brilliant pink. The root may be a branched mass, 

 a plate, or a disc attached to mud, other algae, or 

 rock, whilst the fronds 

 are filamentous, mem- 

 I branous, crustaceous, or 

 calcareous. The asexual 

 organs consist of spor- 

 angia whose entire con- 

 tents in some genera 

 escape as a single non- 

 motile spore. In the 

 majority, however, each 

 sporangium contains four 

 non- motile spores. The 

 sporangia are solitary or 

 grouped in sori, and often 

 sunk in the tissue of the 

 frond or in special 

 branches. The sexual 

 organs are antheridia and 

 procarpia. The anthe- 

 ridia are generally modi- 

 fied terminal branches 

 or special areas in the 

 thai his ( of the more suc- 

 culent forms), from which are derived short rod- 

 like fertilising cells, here called pollinoids. The 

 female organ is a procarp, whose structure varies 

 in complexity in the different orders of Rhodo- 

 phycese. In the simplest condition it recalls 



Kg. 5. Griffithria ittaren 

 ( one-half natural size ). 

 (AfterThuret.) 



Fig. 6. Odmthalia dentata (one-third natural size). 



the female organ of Coleochn-te, and consists 

 of a_ rounded cell with a long filamentous apical 

 portion, the trirhogyne. In higher memliera of 

 the series the trichogyne is separated from that 

 portion of the procarp from which the product* of 

 fertilisation ( i-nrj>orpore) are derived by one or 

 more intermediate cells, the trichophore', and the 

 basal part itself may become multicellular, all or 

 only some of the cells of which produce the pro- 

 435 



ducts of fertilisation. Fertilisation is effected by 

 fusion of a pollinoid with the trichogyne, the 

 immediate result being the 

 formation of a cluster of cells, 

 the carpospores, derived from 

 the fertile cells of the base. 

 These carpospores may form a 

 mulberry-like mass ( Nema- 

 lion), or be enclosed by a 

 loose involucre of filaments 

 ( Griffi thsia ), or by an ovoid 

 capsular investment with a ter- 

 minal pore (Polysiphonia). In 

 others again the collection of 

 carpospores (cystocarp) is com- 

 pletely enclosed within a thick- 

 walled spherical sac (Plo- 

 camium), or may be sunk in 

 the tissue of the frond (Du- 

 montia). The Rhodophycese 

 embrace a large number of 

 orders, the representatives of 

 several of which form well- 

 known objects of interest on 

 the seashore. The best known Fig. 7. Corallina 

 of these perhaps are Carrageen officinalit, a cal- 

 (Chondrus critpiu), Dulse careous seaweed 

 (Rhodymenia palmata), and ( natural size ). 

 Laver (Porphyra laciniata). 

 The genera Callithamnion, Delesseria, Nitophyl- 

 Inm, Plocaminm, and Odonthalia are well known 

 to collectors for the beauty of their fronds. In 

 concluding this article it may lie of interest to point 

 out that the vast collection of feathery plant-like 



Fig. 8. Reproductive Organs of the Rhodophyeee : 

 o, cystocarp of SpermoUiiimnion turneri ; b, cystocarp of Paly- 

 fiphonia vrctolata ; c, cystocarp and antheridiuiu of Calenella 

 opuntia ; d, tetraflporangia of L'tiliitliamnion tenuissimum. 



forms, popularly classed as ' seaweeds ' by seaside 

 visitors and sold as such after being fancifully 

 tinted, are in no respect related to the forms 

 we have been considering, but really belong to 

 the zoophyte division (Hydrozoa) of the animal 

 kingdom. 



For British Seaweeds, see Harvey, Phycolor/ia Britan- 

 niea ; Ciray, British Seaweed* ; Landsborough, Popular 

 History of British Seaweedt. General and Systematic : 

 Agardh, Specie*, Genera, et Ordinet A Itjartim ; Thuret, 

 Etuda Phycologiquet ; Bornet et Thnret, Notci Algolo- 

 giqufi; HtMc\t,Ditifeereialgm; Reinke, Atlas Meerct- 

 algen; Falkenberg in Sohenk's Handbuch der Botanik; 

 Schmitz, Untersuchungen tiber die BefrucMung der 

 Florideen. 



Sea-wolf. See WOLF-FISH. 



