the Colony of Western Australia. 527 



the northern and noi'th-eastem beaches grows abundance of Polyphysa pmiculus, 

 a very remarkable little Alga, known only in this locality, where it was detected 

 by Dr. R. Brown. It is invariably found attached to dead shells, chiefly to the 

 separated valves of a common Venus (like T''. au7-ea ?), and is very frequently in- 

 fested by a peculiar Polysiphonia (P. infestans H.), which I have found nowhere 

 else. Hormosira Lahillardieri, a fucoid plant, resembling strings of beads, and 

 the only representative of the littoral fuci which I have met with, occurs on 

 rocks near high-water mark, and extends to half-tide level. All the other fucoid 

 plants of this coast commence at low- water mark, and are rarely left dry, even 

 at the greatest recess of the tide. The deeper parts of the harbour appear to 

 be occupied by immense strata of Dictyota furcellata, a slender, excessively 

 branched species ; and of Stilophora Ly?igbycfi, with a liberal sprinkling of Hyp- 

 neoe, and of a very luxuriant variety oi Spyridia filamentosa. On the leaves of 

 Zostera, and on the stems of CauUnia antarctica, both which form vast meadows 

 in water from two to six feet deep, grows a profusion of small parasites, and on 

 scattered stones, in the same zone of depth, Laurencia Tasnumica, and Cysto- 

 phyllum niuricatum, flourish abundantly. 



At Middleton Bay is an extensive strand, some miles in length, reaching to 

 the entrance of Oyster Harbour, and a narrow belt of rocky shore at the southern 

 end, where, at the low-water of spring tides, many interesting species of the La- 

 minarian zone may be gathered. EcMonia radiata, the only laminarioid plant of 

 this coast, fringes the whole of these rocks, and extends some distance within the 

 heads of Princess Royal Harbour. Outside the heads, in the more open bay, 

 the leaves are generally rough with prickles, and the whole plant grows stronger, 

 being the state described by authors as E. hiruncinata or E. exasperata ; while 

 in the tranquil water of the harbour the surface of the fronds is generally smooth, 

 being the E. radiata of Agardh. From personal observations I conclude that 

 tliese supposed species are not distinct, as originally stated by Turner. In 

 summer time the rocks at Middleton Bay, between high and low water, are 

 either completely bare, or produce a scanty vegetation of obscure Calothrices; 

 or of a very minute Polysiphonia, with starved varieties of Gelidium conieum ; 

 the power of the sun being probably too great to admit of the growth of a 

 fucoid vegetation, sucli as clothes rocks similarly exposed in colder climates. 

 But in winter these same rocks are all densely covered with Chorda lomentaria 



