ALG.E. 



449 



very interesting as presenting, in a special condition, exactly similar 

 spores, tetraspores, and antheridia to those of the Rhodospermeae, which 

 they thus connect with the Fucaceae, with which they agree in habit and 

 with which they were formerly combined. They belong rather to warmer 

 localities, and are more delicate than the Fucaceae, sometimes, as in 

 Padina, exhibiting attractive colours. They are of no known use. Genera : 

 Dictyota, Lamx. ; Dictyopteris, Lamx. ; Taonia, J. Agh. ; Padina, Adans. 



FUCACFLE. SEA-WRACKS. 



Class Algae, Endl. All Algales, Lindl 



Fig. 611. 



Diagnosis. (Fig. 511.) Olive-coloured Seaweeds of gelatinous, 

 cartilaginous, or horny texture, with 

 a foliaceous or shrub-like or cord- 

 like thallus, attaching itself to rocks 

 by a simple or lobed and ramified 

 discoid base; fructification in recep- 

 tacles formed out of lobes of the 

 fronds (a), the external surface of 

 which is pierced with orifices leading 

 to chambers (conceptacles, b) lined 

 with filaments intermixed with spore- 

 sacs (e) or filamentous antheridia (c), 

 or both of these ; the olive-coloured 

 spores 4 or 8 in a spore-sac, from 

 which they escape when mature, and 

 are fertilized by the active 2-ciliated 

 corpuscular spermatozoids (d) after 

 they are detached from the parent. 

 Illustrative Genera : Sargassum, 

 Eumph. ; Cystoseira, Agh.; Hdlidrys, 

 Lyngb. ; Himanihalia, Lyngb. ; Pyc- 

 nopkycus, Kiitz. ; Facus, L. 



Structure and Life-history. Some of 

 the filaments lining the conceptacles be- 

 come, after a time, swollen and filled with 



brownish matter; this brown matter is de- Organization of Fucacese : A. Halidrys 

 Veloped into 2, 4, or 8 Spores, which escape nttquota, half the nat. size : a, pods or 



from a small orifice at the apex of the con- 

 ceptacle, through which also subsequently 

 pass the tufts of sterile hairs which do 

 not undergo metamorphosis into spores. 

 Sometimes the antheridia are present in the same conceptacles as the 

 sporanges ;. or they are borne on a separate plant (dioecious). The anthe- 

 ridia consist of ovoid cells, some on branched threads and containing a 

 whitish mass, interspersed throughout which are a number of red 

 granules. The antheridia are ejected through the orifice of the concep- 



tacle, the cavity of which is lined by 



(e 8 F ermato - 



