NOTES. 
THE PLURILOCULAR SPORANGIA OF PETROSPON- 
GIUM BERKELEYI. — While collecting Algae in July last year at 
Murlough Bay and the Giant’s Causeway in the County Antrim, 
Mr. E. M. Holmes, with whom I enjoyed the privilege of collecting, 
kindly pointed out to me some specimens of Petrospongium Berlieleyi , 
Naeg., growing on the rocks very near low water-mark at Murlough, 
a little to the east of Miss Clarke’s cottage ; later I found it at the 
Giant’s Causeway, but nowhere was it abundant. 
The late Professor Harvey, writing of this plant (Phycologia 
Britannica, 1846-51, PL CLXXVI), says, ‘On the west coast of 
Ireland it is plentiful in several places, and probably is pretty generally 
distributed along our shores, being overlooked on account of its being 
often nearly the colour of the rock on which it grows, and resembling 
in its fleshy appearance and feel the collapsed body of the common 
Actinia It belongs to the division of Brown Algae or Phaeophyceae, 
which are usually considered to multiply asexually by means of 
zoospores produced in large numbers in unilocular sporangia ; these 
zoospores show a well-marked red eye-spot, two laterally fixed cilia, 
and a chromatophore. A sexual method of reproduction also obtains 
among many genera, consisting in the conjugation in pairs of isomor- 
phous planogametes with the formation of zygotes. To this division, 
the Phaeosporeae, belong the well-known Tangles or Oarweeds of 
our coasts, together with a host of more inconspicuous and delicate 
forms differing very much from one another in habit and mode of 
growth. 
Although each species is supposed theoretically to have both asexual 
unilocular sporangia and sexual plurilocular sporangia or gametangia, 
each cell of the latter rarely giving rise to more than one zoospore or 
gamete, there is a large number of plants in which only one kind 
of reproductive organ has as yet been observed. It was with a view 
of looking for the plurilocular sporangia in Petrospongium, which hitherto 
[Annals of Botany, Vol. XIII. No. LI. September, 1899.] 
