FUCOIDEiE. 



[ 275 ] 



FUCOIDE^. 



croscopic zoospores, which are pear-shaped, 

 with a clear, beak-hke, narrow end, of oUve 

 colour, and have two cilia, not arising from 

 the beak, but from a reddish point on the 

 coloured portion ; one cilium is longer than 

 the other, and directed forwards ; the other 

 is short, and trails behind like a kind of rud- 

 der. Their movements are very active, and 

 they seek the light. When they germinate, 

 they become immoveable and spherical, ac- 

 quire a membranous coat, and emit a tubular 

 prolongation, which soon becomes divided 

 by cross septa, and is developed into a new 

 frond. These plants present, in addition to 

 the oosporanges, another structm-e called by 

 Thuret tricliosporanges, consisting of very 

 slender and usually rather short, jointed fila- 

 ments, in each joint (cell) of which a single 

 zoospore is produced. The trichosporanges 

 occm* in considerable number, occupying the 

 same place as the oosporanges, which they 

 sometimes accompany, but ordinarily only 

 one kind of organ is found on the same plant 

 at the same time. The zoospores are per- 

 fectly similar, except that those produced 

 singly in the filaments are not so large as 

 those developed in large numbers in the 

 large ovate oosporanges. 



The two kinds of sporange producing zoo- 

 spores have been found in the Myriouemaceae, 

 Chordariacese, Sporochnaceffi, Punctariaceae, 

 and Dictyosiphonacese ; in Chorda lomentaria 

 only the trichosporanges, and in the other 

 Laminariacese only the oosporanges have been 

 seen at present. 



The Cutleriacepe present the remarkable 

 phaenomenon of the occurrence of sporanges 

 containing zoospores together with anthe- 

 ridia analogous to those of the Fucacea?. 



(See CUTLERIA.) 



2. The spores occur in the Dictyotaceae 

 and the Fucaceae, as large granular bodies of 

 ovate form, enclosed in a sac or sporange 

 iperispore), andclothedbesidesbya gelatinous 

 coat, called the epispore ; these large spores 

 are always devoid of power of motion. In 

 some cases they are simple reproductive 

 spores, in others they subdivide, after esca- 

 ping fi-om the perispore, into two, four, or 

 eight sporules, each capable of germination. 

 (See Fucus, and figs. 25/, 260.) In the Dic- 

 tyotaceae these spores are collected into defi- 

 nite groups (sori) on the surface of the frond. 

 It is not stated by algologists whether an- 

 theridia have been found here. In the Fu- 

 caceae the spores are found in spherical cavi- 

 ties immersed in the substance of the frond, 

 sometimes occm'ring in all parts, sometimes 



collected in special regions. These cavities 

 communicate with the external surface by 

 pores, and are usually perceptible from the 

 swollen, slimy appearance where they exist. 

 Where no general receptacles exist, the 

 little spherical chambers are excavated in 

 the frond ; where these do occur, as in Fucus, 

 the spherical chambers are attached to the 

 inside of their walls, one beneath each ex- 

 ternal pore. These chambers, called by some 

 scaphidia, by others conceptacles, contain 

 spores or antheridia, or both. The spores 

 occur in sacs consisting of a cell (perispore) 

 springing from the wall of the chamber. 

 (See Fucus.) 



3. The spermatozoids have been met with, 

 as w^ell as zoospores, in the Cutleriaceae. 

 The spermatozoids (or antherozoids, as Thu- 

 ret terms them) exactly resemble those of 

 Halidrys and Pycnophycus, described in the 

 following paragraph. 



In the Fucaceae the spermatozoids or an- 

 therozoids occur with the spores above de- 

 scribed. In Fucus canaliculatus {Pelvetia, 

 Dene, and Thuret) and F. platy carpus, Thu- 

 ret, the antheridia are found, in company 

 with the spores, in the conceptacles ; in the 

 other species of Fucus the two kinds of or- 

 gans are never met with together in the same 

 conceptaele ; in Himanthalia lorea they are 

 on distinct plants ; in Halidrys siliquosa in- 

 termingled, and in Pycnophycus tuberculatus 

 in the same chamber, but not mixed. The 

 antheridia of these plants consist of transpa- 

 rent ovoid sacs, inserted in great number on 

 the branched hairs [paranemata), clothing 

 the inside of the fruit-chambers or scajjhidia 

 (fig. 258). In some genera they have a 

 double coat, in others only one ; when two 

 exist, the inner is expelled as a sac on the 

 ruptiu-e of the antheridium ; when only one 

 exists, the spermatozoids are expelled indi- 

 vidually and freely from the single coat, which 

 always remains attached upon its support. 

 The spermatozoids or antherozoids found in 

 these sacs are little hyaline globules, each 

 enclosing a granule of grey colour in Fucus 

 canaliculatus, red-orange in all other species 

 of Fucus and other genera. They bear two 

 locomotive cilia, very slender, and of unequal . 

 length. The form of the corpuscles and the 

 arrangement of the cilia differ in different 

 genera. In all the species of Fucus the 

 spermatozoids are of the shape of little 

 bottles, the neck of which, always foremost 

 in the movement, bears the shortest cilium ; 

 the longer arises from the coloured granule, 

 and trails behind. In Halidrys, Pycnophycus, 



t2 



