Clare Island Survey — Marine Algae. 16 141 



Beautiful specimens, perfectly spherical in form and sometimes as much as 

 20 cm. in diameter, may be seen floating in with the tide during May. No 

 plants were noted in the rock-pools on Clare Island. 



Boraetia secundiflora Thur. 



Bornetia is one of the most interesting additions to the Irish flora. It is 

 abundant in the Mediterranean (south France), and common in the Biarritz 

 neighbourhood. 1 1 extends up the Atlantic coast as far north as Normandy 

 and Brittany, and is found as a very rare plant on the shores of Devon and 

 Cornwall. Two fine plants were collected in a deep pool on Clare Island, 

 in July, 1909, and though neither bore mature fruit, there can be no doubt 

 as to their identity. The pool was searched on each subsequent visit ; but, 

 with the exception of a small frond found in August, 1911, no further 

 specimens were observed. 



Callithamnion byssoides Arn. 



The specimens referred to this species agree well with those from 

 Devonshire collected by Mrs. Griffiths, and with the plant as generally 

 understood in this country. In general habit it bears a very close resem- 

 blance to C. corymbosa, and even with a lens it is not easy to separate the 

 two. The distinctive feature is the irregular pinnate branching, which 

 connects it in the other direction with C. roseum. From the latter it is 

 marked off by the very much more slender growth, and by the tetraspores 

 being usually single on the pinnae. The form of the cystocarp is also 

 different. 



C. byssoides is common in Clew Bay and Achill Sound (as a spring 

 and early summer plant), occurring as an epiphyte on various algae in 

 the low-littoral and sub-littoral region. It is very closely allied to, if 

 not identical with, C. Fwcellariae of the Swedish botanists. 



C. scopulorum Ag. 



I follow Borgeseu in regarding this plant as a distinct species, which 

 differs from C. polyspermum in its dwarf size, absence of cortication, and 

 saxicolous habit. It is abundant on Clare Island, on moderately exposed 

 rocks, but, owing to its minute size, is not conspicuous. 



C. arbuscula Lyngb. 



An alga belonging to the boreal group, but abundant on Clare Island. 

 It apparently occurs on all the Irish coasts, but is quite absent on the south 

 of England (see pp. 164 and 169). 



