THE GENUS POLYSIPHONIA. 303 
The various species of Polysiphonia exhibit such diversity of form depen- 
dent on the conditions under which they are growing that it seems unneces- 
sary to create new species for these forms until they have been shown to 
possess some stability. 
Habitat. Occurring on rocks, stones, and on other algæ such as Chorda 
filum near low-water mark. Rather rare. 
British Records. Orkney Islands, Peterhead, Elie, Earlsferry, Berwick, 
Whitley, Roker, Kent, Sussex, Hants, Dorset, Devon, Cornwall, Carnarvon, 
Isle of Man, Arran, Bute, Cumbrae, Howth, Bantry, Ferriter’s Cove, Round- 
stone, and the Channel Islands. 
Distribution in Europe. Generally distributed over the coasts of Northern 
Europe. 
B. More than four primary pericentral siphons. 
1. P. Broniæt Grev. in Smith’s Engl. Flora, v. 1833, p. 328. 
Grammita Brodiei Bonnem. H ydroph. loc. 1822, p. 31. 
P. penicillata Kütz. Spec. Alg. 1849, p. 827. 
P. polycarpa Kütz. Tab. Phye. xiv. 1864, p. 1, tab. 2 (e-g). 
P. callitricha Kütz. l. e. tab. 2 (a-d). 
References. Agardh (2) ii. p. 993 ; De Toni (22) iv. p. 947; Hauck (81) 
p. 237. 
Icones. Harvey, Phye. Brit. 1846-51, pl. 195. syn. 118. Kützing, Tab. 
Phye. lc. Lvsiecata. Wyatt, Alg. Damnon. no. 83. 
DzscnrPrioN.— Habit. Plants branched from the base, frequently showing 
a distinct main axis. Branching irregular or pseudo-dichotomous, densely 
clothed with tufted ramuli. Substance cartilaginous, but flaccid in the 
ramuli. Siphons. 6-8 primary pericentral siphons, alternating with which 
oceur the same number of secondary siphons bounded by a band of corti- 
eating cells. Colour. Dark purplish-red, becoming much darker in drying. 
Anatomy. Articulations of the main axis and principal branches entirely 
obscured by the cortication ; articulations of the ramuli about as long as 
broad. Attachment organ. Young plant attached to the ‘substratum by a 
number of rhizoids formed by the longitudinal proliferation of the siphons 
and by the elongation of the corticating cells, a certain amount of mechanical 
coherence resulting in the formation of a dise as in P. elongata, although the 
individual rhizoids are looser. Later, certain of the procumbent branches 
form rhizoids by the lateral elongation of the corticating cells, thus giving 
additional strength to the organ. The form of the attachment organ thus 
comes intermediate between the P. nigrescens and P. elongata types. Repro- 
ductive organs. Tetraspores intercalary in development, borne in swollen 
ramuli. Cystocarps ovate in form and shortly stalked, developed in large 
numbers on the ramuli. 
P. Brodiæi Grev. differs anatomically from P. Brodiwi Aresch., the latter 
having as many as 16 siphons in the main thallus and 12 in theramuli. The 
ramuli are very numerous, giving the plant a distinctive tufted appearance. 
