THE GENUS POLYSIPHONIA. 287 
numerous ramuli. Filaments attenuate upwards, varying from :5—05 mm. 
in diameter. Siphons. 4 pericentral round small central. Colour, Reddish- 
brown. Anatomy. Articulations visible throughout the plant ; 2-3 times as 
long as broad in the middle parts of the main branches, diminishing to a 
length equal to their breadth in the ramuli, and shorter than their breadth 
near the attachment organ. Tips of branches clothed with dichotomising 
fibrille during the summer. Attachment organ. Young plant attached by 
rhizoids with dises at their apices, the rhizoids being formed by longitudinal 
proliferation of pericentral siphons. Later, rhizoids produced by pericentral 
siphons of procumbent branches. Reproductive organs. Tetraspores borne 
in swollen and distorted ramuli. Antheridia cylindrical, obtuse, rounded 
at their apices, borne on the dichotomising fibrille. Cystocarps very 
shortly stalked, almost sessile, ovate, with short ostiole which is frequently 
sinuous. 
Habitat. Occurring on rocks and stones near low-water mark. Rare. 
British Records. Plymouth, Trevone Bay, and Ilfracombe. 
Distribution in Europe. In France on the inter-tidal roadway called Le 
Rhun, connecting the mainland at Saint-Vaast la Hougue with the little 
island of Tatihou. 
4. P. spıraLıs Batten, spec. nov. 
Frondes rubiginose-fuscescentes, cæspitosæ, pollicares vel usque ad 25 mm. 
altæ, e filis repentibus orte, irregulariter divisæ, chartæ adhaerentes, Rami 
inferiores repentes substrato adfixi, copiose rhizoidiphori, articulis instructi 
diametro brevioribus, siphonibus rectis. Rami ascendentes et erecti articu- 
lis instructi diametro usque ad 3-plo longioribus et siphonibus valde sed 
regulariter contortis. Articuli quatuor siphonibus instructi, circa siphonem 
centralem dispositis, sectione transversali quadratum formantes, semper 
ecorticati. Tetrasporangia in ramulis non contortis, articulis iterum brevi- 
oribus. Antheridia et eystocarpia non visa. 
Habitat ad saxa, in regione inferiori litorali, ad Durlston Head, Swanage, 
Britannis. 
Legit auctor. 
DescRIPTION.— Habit. Occurring in small tufts rarely more than an inch 
in height. Branches either arising alternately or showing a marked 
tendency to a unilateral arrangement, the latter being accentuated in the 
parts bearing tetraspores. Ramuli often backwardly directed, though not 
as conspicuously as in P. macrocarpa. Substance gelatinous, adhering 
to paper. Siphons. 4 pericentral round large central. Colour. Brownish. 
Anatomy. Articulations no longer than their breadth in the procumbent 
parts of the plant, 3 times as long as broad in the upright branches, dimin- 
ishing in the ramuli. Pericentral siphons parallel to the long axis of the 
filament in the lower parts of the plant and in the ramuli, but spirally 
