272 DR. LILY BATTEN ON 
thallus, which in many of the essential points is curiously similar throughout 
the genus. The study of the attachment organ has been of considerable 
interest, largely on account of the gradual increase in complexity which is 
visible in the group. The form of the attachment organ has been correlated 
with the general anatomy of the species, and the parasitism of P. fastigiata 
has been proved. 
| The elimination of false synonyms has been possible after consulting the 
records and collections at Kew and the Natural History Museum. An attempt 
has also been made to bring together those plants which are forms of some 
previously recorded British species, but through environmental modification 
have been given a new specific name, or have been re-named by British 
workers without due consultation with the records of foreign species. A key 
to the species, based on purely vegetative characters, has also been 
compiled, and. P. spiralis is described for the first time. In order that 
the paper may be more complete for reference, a summary of the literature 
on the development of the reproductive organs of the genus has been 
inserted. 
The paper deals exclusively with the genus Polysiphonia, of which 24 
species are recorded, types which are now grouped with the Pterosiphonias 
having been reserved. The two groups are distinguishable by their 
respective methods of branching. In the Pterosiphonias the branching is 
markedly pinnate throughout the plant, both branches and ramuli being set 
at acute angles. 
My thanks are due to Professor O. V. Darbishire for his advice and help, 
and for having placed his valuable library at my disposal. I am also 
indebted to Mr. A. D. Cotton for material from Weymouth and Poole, to 
Mr. W. Searle for specimens from Love and Plymouth, and to Mr. W. P. 
Hiern for specimens of P. variegata and P. subulifera from the herbarium 
of the Rev. W. S. Hore, and for his kindness in facilitating my access to 
the herbarium of Mrs. Griffiths at Barnstaple. I must also express my 
thanks to Miss Blackburn for material from Cullercoats, to Dr. A. H. Church, 
and to Mr. E. M. Holmes for valuable information. Any artistic merit 
which the figures may possess is largely due to the experienced advice and 
criticism of my friend, Mr. C. Hanney, of the Bristol School of Art. 
I should also like to take this opportunity of expressing my thanks to 
the Committee for Industrial and Scientific Research, and to the Colston 
Research Committee for financial assistance. 
HISTORICAL. 
The genus Polysiphonia was originally described by Agardh in 1817 under 
the name of Hutehinsia, but that name is inadmissible owing to a group of 
the Cruciferæ having been previously given that generic name by Robert 
Brown. In 1822 Bonnemaison substituted the term Grammita for that of 
