72 A SUPPLEMENT TO THE * FLORA VECTENSIS,*
receive the full influence of the sun's rays, which certainly affects the mean temperature.
The Algic of the " Maidens," with few exceptions, have a wide rano;e in latitude and louf^itude on the British and Irish coasts ; Alaria and Oclon- thalia are chiefly confined to the Northern shores.
As to the relation betvveen the kind of rock and the distribution of Alj?fe, it may be sufficient to observe that the more abundant and widely diffused are found indift'orently on rocks of the most opposite character; that liabitat does, however, modify the composition of at least one common species seems proved by the following instance. "VVlien passing the co;ist at Bay of Nigg, near Aberdeen, in September last (1870), I observed an iron chain newly brought to shore which had been during six months in four to five fathoms water, it was completely covered by the Rhodi/mejiia palmata ; attached to tliis chain there was a piece of hempen rope, about three feet in length, which had a crop of Polyuphonia Brodirei ; these were the only species, and each was strictly confined to the chain in the one case, and to the rope in the other. The Polysiphonia was of good size, nearly as large as it occurs on the neighbouring rocks ; the Rhodymema was dwarf, two or three inches, paler and more delicate than usual ; of the last I collected sulhcient for analysis, and am indebted for a report to my friend and former pupil, J. C. Brown, D.Sc. Lond., and Lecturer on Toxicology, Medical School, Liverpool ; he was very careful to avoid any source of fallacy.
Rhodymenia from iron chain, Iron = 0-01 13 per cent, of dry plant, or 0'235 per cent, of tlie aslies. RJiodymenia from granite rocks. Bay of Nigg, Iron = 00035 per cent of the dry plant, or 0"056 per cent, of the ashes. It can scarcely be that in this case each plant "selected" its special ha- bitat; Rhodymenia is a common perennial species, the Polysiphonla appears only toward the end of summer. The fishermen at the salmon station assured me that chain and rope were quite clean when put into the sea; it is probable that the piece of rope had been in some way bedded in sancl or mud, which having been, towards the end of the season, washed away by currents, the Polysiphonla grew on it, the chain having been previously covered with a thick crop of the Rhodymenia.
��A SUPPLEMENT TO THE 'FLORA VECTENSIS.'
By Alexander G. More, E.L.S., M.R.l.A.
During the fourteen years which have elapsed since the publication, in 1856, of Dr. Bromfield's 'Flora Vectensis,' several plants have been added to the list, and the discovery of many new localities for rare species has rendered the botany of the Isle of Wight much better known. The present seenis a good opportunity for bringing together various contribu- tions received from other botanists, which, joined to the results of my own observations during seven years' residence at Bembridge, from ISo'G to 1862, will serve, in some measm-e, as a continuation of the successful hibours of the late Dr. Bronifield.