MELANOSPERME.E. 95 



occur gregariously in extensive patches, covering rocks 

 of Fuci with a bright green fringe. 



I shall now notice a few of the more common of the 

 Olive-coloured group of Sea-weeds, or Melanospermece, 

 so called, because their reproductive grains, or spores, 

 are of a dark colour, or so opaque that they appear dark 

 when seen by transmitted light. This group consists 

 of much more perfectly-formed plants than those we 

 have just noticed. They are, also, commonly of much 

 greater size: the largest of all sea-plants belong to 

 them. The olive sea-weeds commence to grow, as I have 

 already said, just within the margin of the tide, and 

 they extend throughout the whole of the littoral zone, 

 and to the depth of one or two fathoms below low- 

 water-mark. The first species we meet with is Fucus 

 canaliculatus, the smallest and most slender of the 

 British Fuci. It grows in scattered tufts, one or two 

 inches high, on rocks about high-water-mark, and is at 

 once known by having narrow, channelled stems and 

 branches, without air-vessels. It rarely grows in water 

 of a greater depth than three or four feet, and never in 

 places where it is not exposed for several hours daily to 

 the air. To it succeed Fucus nodosus, a large species, 

 with leathery, thong-like stems, distended at intervals 

 into knob-like air-vessels, and covered in winter and 

 spring with bright-yellow berries ; and F. vesiculosus, a 

 more membranous kind, having a forked leaf, traversed 

 by a midrib, and bearing numerous air-vessels in pairs, 

 at either side of the rib. This species is gregarious, 

 covering wide patches of rock from a foot or two be- 

 low high-water to low-water-mark. Growing thus, at 



