Page:Journal of botany, British and foreign, Volume 34 (1896).djvu/377

 new marine alg^. 849 Possible Extinction of Indigenous Species. It is scarcely to be feared that any large number of indigenous species will become exterminated unless under special conditions not yet realized. It has been shown that the aspect of vegetation over large areas may be changed by displacement, but it does not follow that this would involve the absolute extinction of many, or even of any, indigenous species. Displacement rarely passes into absolute replacement ; after it has reached a certain stage the invaders lose a portion of their vigour, and become less encroaching ; a portion of the indigenous vegetation becomes gradually inured to light and air, the severity of the struggle becomes less intense, and a gradual amalgamation takes place between the invaders and the invaded, which of itself facilitates the preservation of many of the more delicate kinds, while those less fitted to hold their place in the contest become restricted to those habitats which are of a peculiarly favourable character. The danger of extinction is greatest for those endemic species which are so remarkably local ; for instance, Epilobium brcvipes, restricted to a solitary habitat on Mount Torlesse, and another in the Awatere, may at any time be destroyed by an unusually hungry rabbit or sheep, and one of the most interesting plants in the colony blotted out of existence. Clianthus piiniceus is already restricted to one or two islets where sheep are unknown, and owes its preservation in a wild state to their absence. Loyania depressa, Myrsine montana, and Ahrotanella pusilla are in exactly the same position as Epilobium brevipes. The list might be increased, but it is needless to mention others. NEW MARINE ALGiE. By E. M. Holmes, F.L.S. Since the publication in the Annah of Botany (viii. 336-342) of some new Marine Algae from Natal, I have had the opportunity of further examining some of the material sent by Dr. Becker, and have found two other new species and the fructification of a third, all of which can now be referred to the proper genus. 1. Ectoclinium Kowiense, n. sp., fronde membranacea plana, lineari, pluries tri-dichotoma flabellato-subcorymbosa, ramis axillis rotundatis, supeiioribus subasqualibus divaricato-patentibus, terminalibus vage dentatis, subdivergentibus. Hab. The Kowie, Dr. H. Becker, This species differs chiefly from the Australian species E. dentatum in the absence of a visible nerve, and in the uniform width and thickness of the divisions of the frond, which are narrower only at the tips. The remarkably rounded axils and spreading branches give the aspect rather of a very narrow Rhodo- phyllis than that of an Ectoclinium, but the nemathecioid sorus of tetraspores at once distinguishes the plant from the genus Rhodo-