8 Dansk Botanisk Arkiv, Bd. 2. Nr. 6. 



while further out they would be covered at high tide by more 

 water than is usually the case where they grow. Other un- 

 favourable factors may be, that the water falls and rises with 

 great force, and that its movements stir up the fine mud particles 

 and greatly reduce the transparency of the water. Of course 

 these are only suppositions, but the fact remains that sea-grasses 

 do not seem to grow along the north coast, and also that Algæ 

 are very scarce .there. 



Along the west coast the case is quite different. As Mrs. 

 C. M. G. Dakin states (in the Handbook and Guide to W. A. 1914, 

 p. 73), there is no strong tide here. "The average tide at Fre- 

 mantle is only about one or two feet". Here we find a well- 

 developed sea-grass vegetation in the more sheltered places, and 

 in many cases it covers wide areas, as at Shark's Bay. 



The following are notes from my diary on the occurrence of 

 sea-grasses at different places of the west coast of W. A. 



1. The coast of the Cave District off the Yallingup 

 Cave (between Cape Naturaliste and Cape Leeuwin), Sept. 

 26th 1914. The coast is partly sandy, partly rocky. The rocks 

 consist of a calcareous conglomerate of grains of sand bound 

 together by lime. In this rock formation numerous pools and 

 flats with shallow water are found; they are protected by the 

 outer fringe of rocks from the enormous force of the ocean 

 waves, and harbour a rich algal vegetation in which Cystoseira 

 species and Corallinaceæ are dominant. The algæ grow fixed to 

 the rocks bordering the pools, while the sandy bottoms are 

 largely covered with Cymodocea antarctica and Halophila ovalis. 



At the Cottesloe beach near Fremantle the conditions were 

 much the same, but Halophila was not seen there, only Cymod. 

 antarctica. 



2. Gerald ton, Octob. 28th and 29th 1914. Many sea -grasses 

 were thrown ashore and formed a low wall on the open sandy 

 coast. I noticed a few specimens of Halophila ovalis and Cy- 

 modocea antarctica, some specimens of Cym. isoetijolia and great 

 masses of Posidonia australis, leaves and fruits. 



The sea bottom, seen from the jetty, is barren naked sand 

 close to the shore, but outside this a dense covering is seen 

 over wide areas, probably of Posidonia. 



3. Sharks Bay at Carnarvon, Octob. 31st 1914. Sharks Bay 

 is rather shallow, and in calm weather when steaming over the 

 bay from Cape Inscription to Carnarvon the sea bottom was 

 visible nearly the whole time. The bottom is plant-covered 



