12 FUCACEjE. 



the axils or along the edges of the leaves or branches. Air- 

 vessels are present in almost all, either as bladdery swellings 

 of the stem or branches (as in Fucus), or as distinct organs 

 (in Saryassum, &c.), stalked, and mostly springing from the 

 same part as the fructification. Receptacles of the fruit 

 mostly more or less distinguishable from the barren portion 

 of the frond, swollen, succulent, often filled with slimy mu- 

 cus, either formed from the metamorphosed ends of the 

 branches, or evolved from the axils or sides of the branches 

 or leaves. These receptacles (or the whole frond in genera 

 which have no proper receptacle) are pierced by minute 

 pores, which communicate with small, spherical chambers, 

 formed by an introflexion of the walls of the receptacle, at 

 the points where they occur. The little chambers (called 

 conceptacles by some writers, scaphidia by others) contain 

 sometimes spores, or reproductive bodies analogous to the 

 seeds of more perfect plants ; sometimes antheridia, sup- 

 posed to be analogues with stamens ; sometimes both organs 

 in the same chamber. The spores spring from the sides of 

 the chamber. One of the surface-cells being fertilized, gra- 

 dually enlarges, projects from the wall of the chamber, be- 

 comes more or less obovate, and finally is converted into a 

 perispore, or membranous, transparent case, in which is con- 

 tained the spore or spores. These last are formed from the 

 matter contained within the enlarged cell. At first the con- 

 tents are nearly fluid, of a pale olive colour : gradually they 

 acquire density, become darker, and at length are consoli- 

 dated either into a single sporule (as in Cystoseira, Halidrys, 

 &c.), or formed into two, four, or eight sporules (as in Fucus, 

 Himanthalia, Sec.). The antheridia are borne on branching, 

 jointed threads, called paranemata, which rise, like the 

 spores, from the walls of the conceptacle, and commonly fill 

 the greater part of its cavity. Each antheridium is an ob- 

 long cell, forming the terminal articulation of the branches 

 of the paranemata, and is filled with minute, orange-coloured 

 bodies (called sporidia by 3. Agardh) closely resembling the 

 zoospores of the lower Alga?, and, like the latter, endowed 

 with spontaneous movements. The motive organs are vibra- 

 tory hairs or cilia, with two of which each little body is fur- 

 nished. The fronds of many species have numerous mu- 

 ciferous pores, analogous to the pores of the conceptacles, 

 but not leading to any internal cavity : from these issue 

 bundles of transparent filaments, whose use is unknown. 



