FUCOIDE^, 



[ 338 ] 



FUCOIDE.^. 



fi'ond. In some cases the sporanges are 

 multilocular {t}-ichospo)-anffes) , consistmg of 

 very slender, and usually rather short, j ointed 

 filaments, in each joint (cell) of which a 

 single zoospore is produced. These occur in 

 considerable number, occupying the same 

 place as the unilocular kind, which they 

 sometimes accompany ; and the two forms 

 appear to pass one "into the other. The 

 zoospores are perfectly similar, except that 

 those produced singly in the filaments are 

 not so large as those developed in large 

 numbers in the large, ovate, unilocular 

 sporanges. 



The two forms of sporange producing 

 zoospores have been found in the Myrione- 

 mapege,OhordariaceEe, Sporochnacese, Punc- 

 tariaceae, and Dictyosiphonacepe ; in Chorda 

 lomentaria only the multilocular, and in the 

 other Laminariacese only the unilocular, 

 have been seen at present. 



The Cutleriacese present the remarkable 

 phenomenon of the occurrence of sporanges 

 containing zoospores together with anthe- 

 ridia analogous to those of the Fucace^. 



(See CUTLERIA.) 



Those Fucoidese in which the repro- 

 duction is effected by zoospores only, form 

 Thuret's group of Phseosporese. 



2. The spores occur in the Dictyotaceje 

 and the Fucacece, as large granular bodies 

 of ovate form, enclosed in a sporange or 

 oogonium, and clothed besides by a gela- 

 tinous 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 es- 

 caping from the perispore, into two, four, or 

 eight sporules, each capable of germination. 

 (See Fucus, and figs. 253, 256.) In the 

 Dictyotacefe these spores are collected into 

 definite groups {sori) on the surface of the 

 frond. In the Fucaceae the spores are 

 fovnid in spherical cavities immersed in the 

 substance of the frond, sometimes occurring 

 in all parts, sometimes collected in special 

 regions. These cavities communicate with 

 the external surface by pores, and are usually 

 perceptible from the swollen sliiny appear- 

 ance where they open. Where no general 

 receptacles exist, the little spherical cham- 

 bers 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 external pore. 

 Tliese chambers, called by some scaphidia, 

 by others concepfacJes, 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. Spermatozoids have been met with, as 

 well as zoospores, in the Cutleriacese. The 

 spermatozoids or antherozoids exactly resem- 

 ble those of Halidrys and rycnoplujcas, 

 described below. 



In Dictyota the spermatozoids occur on 

 separate plants, in antheridia grouped in 

 sori like the spore-fruit. 

  In the Fucacefe the spermatozoids or 

 antherozoids occur with the spores above 

 described. In Fucus canalicidatus {Pelvetia, 

 Dene, and Thuret) and F. plntycarpus (Thu- 

 ret) the antheridia are found, in company 

 with the spores, in the conceptacles ; in the 

 other species of Fucus the two kinds of 

 organs are never met with together in the 

 same conceptacle ; in Himanthcdia lorea 

 they are on distinct plants, in Halidrys 

 silicpiosa intermingled, and in Pycnophycus 

 tuherculatus in the same chamber but not 

 mixed. The antheridia of these plants 

 consist of transparent ovoid sacs, inserted 

 in great number on the branched hairs 

 (para7icmata) (fig. 254) clothing the inside 

 of the fruit-chambers or scaphidia. In some 

 genera they have a double coat, in others 

 only one ; when two exist, the inner is 

 expelled as a sac on the rupture of the an- 

 theridium ; when only one exists, the sper- 

 matozoids are expelled individually 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 granide of grey colour in Fucus 

 canalicidatus, red-orange in all other species 

 of Fuctis and other genera. They bear two 

 locomotive cilia, verj' slender, and of unequal 

 length. The form of the corpuscles and the 

 arrangement of the cilia difl^er in difterent 

 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, 

 and Cystoseira, the corpuscle is oval or 

 spherical in one dimension, and compressed, 

 sometimes a little convex, in the other; 

 both the cilia are inserted on the red granule, 

 and during the locomotion the corpuscle 

 turns upon its own axis, with the longer 

 cilium in advance, vibrating with rapidity, 

 while tlie shorter is motionless. In Himan- 

 thcdia the antheridia have a double coat; the 



