new marine alg.e. 349 



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, tiie 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. hrevlpes, 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. 

 (iianthiifi puniceus is s^heady restricted to one or two islets where 

 sheep are unknown, and owes its preservation in a wild state to 

 their absence. Lo(jania depressed, Mi/rsine mnntana, and Abrotanella 

 jnisilla are in exactly the same position as Epilobium, hrevipes. The 

 list might be increased, but it is needless to mention others. 



NEW MARINE ALG^. 

 By E. M. Holmes, F.L.S. 



Since the publication in the Annals of Botany (viii. 336-312) of 

 some new Marine Alga3 from Natal, I have had the opportunity of 

 further examining some of the material sent by Dr. Decker, 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 fiabellato-subcorymbosa, ramis 

 axillis rotundatis, superioribus subfequalibus divaricato-pateiitibus, 

 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 tlie aspect rather of a very narrow Uhodo- 

 p/tijUis than that of an Ectoclinium, but the nemathecioid sorus of 

 tetraspores at once distinguishes the plant from the genus RJiodo- 



