FTTCOIDE^E. 65 



in the sea and on the sea-shore. They are of an olive- 

 green or olive-brown colour, and usually become 

 darker on drying. 



Fucus vesiculosus, with its parallel-sided or linear 

 olive-brown fronds, is known to every one as the sea- 

 weed which is hung up to act as a weather-glass. The 

 fronds have a central stout vein, or midrib, and scat- 

 tered air-bladders, mostly in pairs. 



The fructification consists of yellowish oval enlarge- 

 ments of the ends of the fronds, called the receptacles 

 (fig. 16) ; but these are somewhat variable in form, 

 being often angular or truncate. On holding one of 

 the receptacles to the light, it will appear to contain 

 a number of little grains imbedded in its substance, 

 slightly projecting above the surface, and in the centre 

 of each is a minute dot or pore. These grains are 

 the capsules, or conceptacles, and contain the spores. 

 The substance of the receptacles is composed of a 

 beautiful network of colourless, jointed, cellular fibres 

 (figs. 17 a and 18 a), the meshes of which are filled with 

 a transparent gelatinous substance ; but immediately 

 around the conceptacles the cells are shorter and 

 more closely packed. The spores (fig. 19) are arranged 

 in the conceptacles in a radiate manner; they are 

 brown, and surrounded by a colourless sac, called the 

 perispore (Kepi, around, (nropa, seed) ; and between 

 them are numerous slender, colourless, jointed fila- 

 ments, the paraph'yses. The spores are not, how- 

 ever, truly single spores, for they ultimately divide 

 into eight segments or sporules, each of which is 

 capable of producing a new plant. 



In the conceptacles of some fronds of Fucus no 

 spores will be found, the conceptacles (fig. 18) being 

 filled with elegantly branched colourless filaments 

 (fig. 20), the ends of many of them being distended 

 into little yellowish sacs ; these are the antherid'ia. 

 The antheridia contain large numbers of exceedingly 

 minute spermatozoa, furnished with two cilia, and 



