306 Transactions. — Botany. 



was torn from the coast-line, carrying with it many epiphytic 

 species, it might remain an indefinite time in the ocean, 

 breaking up under the influence of the waves, &c, growing 

 and carrying with it a colony of delicate epiphytes, some of 

 which might thus in the course of time be drifted on to the 

 shores of other lands. 



It is to be remembered that a seaweed having reached a 

 new and suitable habitat has not necessarily to contend with 

 species already occupying the coast. There is always plenty 

 of room for it to live — plenty of unoccupied and suitable posi- 

 tions in rock-pools and in the neighbourhood of the tidal area. 

 The flora of the sea does not clothe the rock-surface with a 

 mantle as the herbage does the land. Every heavy gale with ' 

 spring-tides tears hundreds of tons of Algae from the rocks, 

 leaving plenty of bare surface for newcomers or for germinat- 

 ing plants. What are the chief factors in the struggle for 

 existence amongst marine plants I do not know ; but it can 

 scarcely be in the successful crowding-out of weaker competi- 

 tors. Possibly the power of clinging successfully to the rocks 

 is one of the chief of them ; but, whatever they may be, we un- 

 doubtedly frequently find species restricted to a definite area. 



In New Zealand we have many long stretches of sand and 

 shingle that are practically marine deserts as far as the Algae 

 are concerned. Thus, on the west coast of the North Island, 

 from Paikakariki northward to Taranaki Province, there is an 

 unbroken barren beach. Now, in the neighbourhood of the 

 Sugarloaves, at the New Plymouth Breakwater, the common 

 form of Carpophyllum is the one figured as Sargassum phyllan- 

 thum, pi. vii., " Atlas Botanique : Voyage de ' l'Astrolabe.' " 

 This plant, however, is quite distinct from the true Carpo- 

 phyllum phyllanthum, and is either a neglected species or a 

 strongly marked variety of G. maschalocarpum. From Pai- 

 kakariki southward the ordinary form of C. maschalocarpum, 

 together with C. phyllanthum, is common ; and on this portion 

 of the coast I have only found the New Plymouth form on 

 rare occasions in drift-weed on the beach at Ohiro Bay, 

 whither it may have come with the current from Taranaki. 

 Thus a sandy track here separates two distinct and practically 

 discontinuous varieties. Climate, which, of course, is the 

 main agent in determining distribution along a continuous 

 coast-line, can scarcely be said to play a part here, much less 

 in the case of Lessonia varieyata (J. Ag.). This is abundant in 

 deep tidal pools near Wellington Heads, and it extends along 

 the coast to some little distance past Cape Terawhiti, when it 

 disappears, although the coast-line continues of the same 

 character northward as far as Pukerua. Its place is partially 

 taken by Ecklonia. Here it is extremely difficult to account 

 for the local distribution. 



