527 
the Colony of Western Australia. 
the northern and north-eastern beaches grows abundance of Polyphysa pmiculus, 
a very remarkable little Alga, known only in this locality, where it was detected 
by Dr. E. Brown. It is invariably found attached to dead shells, chiefly to the 
separated valves of a common Venus (like V. aurea f), and is very frequently in- 
fested by a Polysiphonia (P. infestans H.), which I have found nowhere 
else. Ilormosira Lahillardieri, a fucoid plant, resembling strings of beads, and 
the only representative of the littoral fuel 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 Lyngbyoei., with a liberal sprinkling of Hyp- 
nece, and of a very luxuriant variety of Spyridia filamentosa. On the leaves of 
Zostera.^ and on the stems of Caulinia 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 Tasmanica, and Cysto- 
phyllum muricatum.^ 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. EcUonia radiata^ the only laminarioid plant of 
this coast, fringes the whole of these rocks, and extends some distance within the 
heads of Princess Eoyal Harbour. Outside the heads, in the more open bay, 
the leaves are generally rough Avith 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 
these 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 corneum ; 
the power of the sun being probably too great to admit of the growth of a 
fucoid vegetation, such as clothes rocks similarly exposed in colder climates. 
But in winter these same rocks are all densely covered Avith Chorda lomentaria 
