972 



XIV. A.LGM. 



antherozoids containing a red globule having the power of motion, and furnished 

 with 2 vibrating hairs, the one anterior, the other posterior. 



SECTION I. LAMINAEIE^E. Reproductive organs superficial (sort) ; spores 

 usually mobile, germinating without apparent previous fertilization. 



Scytofeiphon. 

 Phyllitia. 



Punctaria. 

 Litosiphon. 



Desmarestia. 



Dictyosipbon. 

 Aglaozonia. 



Ectocarpua. 

 Streblonema. 

 Myriotrichia. 

 Girnudia. 



Sphacelnria. 



Cladostephus. 



Arthrocladia. 



Myrionema. 

 Elachista. 



Alaiiii. 

 Coataria. 

 Agarum. 

 Tbalassiophyllum. 



Dictyota. 

 Taonia. - t 

 Padina. 

 Dictyopteria. 



SECTION II. FUCACE^E. Reproductive organs $ and ? contained in concep- 

 tacles ; antherozoids furnished with hairs ; spores motionless. 



PRINCIPAL GENERA. 



Fucua. 



Pelvetia. 



Urvillea. 



Cyatopbora. 



Landsburgia. 



Cytoseira. 



Ilalidrya. 



Sargaaaum. 



Myriodeama. 



Ilimanthalia. 



Splacbnidium. 



Bloavillea. 



In tbe first aection of Phaosporea the aporangia are superficially and irregularly diatributed over the 

 aurface of tbe frond, like sori ; from these aporangia eacape ovoid zoospores, terminated by haira and 

 moving actively, -which germinate immediately they become fixed. In the aecond section of Phaosporeee 

 (Fucacea, properly called, or Wrack) the fructification usually corresponds to tubercles, dispersed over the 

 frond, or united on special organa, terminal, or arranged in axillary racemes. Each tubercle answers to a 

 fructiferous cavity or conceptacle in the thickness of the frond ; this cavity contains a gelatinous matter 

 and beara on its inner wall when young a sort of hairs or transparent filiform cells. At the period of 

 reproduction, such of these hairs (sporangia, perispores) as are to fructify, swell, and become filled with 

 brownish matter. This becomes organized into reproductive bodies, which escape by a amall orifice in 

 the centre of the tubercle, and aeon divide into 2-4-8 spores, which quickly germinate. There remains 

 nothing in the cavity but the torn mother-cells (penspores or sporangia), and the other sterile cellular 

 huirs, which lengthen into little tufts, and also issue in succession through the same orifice. Sometimes 

 the antheridia exist in the same conceptacle with the sporangia, and the plant is monoecious ; sometimes 

 the antheridia and sporangia are borne upon distinct individuals, when the plant ia dioecious. The 

 conceptaclea containing the antheridia are generally recognizable by their orange colour. The antheridia 

 consist of ovoid vesicles, containing a whitish mass, sprinkled with red granules: they are borne upon 

 branched chambered hairs. "When the plant is exposed to the air, the antheridia are expelled in a mass 

 through the orifice of the conceptacle, and at their extremities issue numerous transparent lagenifonn 

 antherozoida, moving rapidly ; each usually contains a red granule, forming a dorsal protuberance ; the 

 locomotive organs consist of two unequal very mobile hairs, the shortest in front, the other dragging 

 behind tbe body of the antherozoid. In the conceptacles where the sporangia and antheridia are united 

 the latter line the upper half, near the opening, and the sporangia occupy the bottom of the conceptacle. 



