300 DR. LILY BATTEN ON 
in form, and borne on apical fibrillæ at the tips of branches. Cystocarps 
stalked, ovate, with large open ostiole, borne on upper parts of branches and 
ramuli. — 
P. jibrata is usually darker in colour than P. urceolata, and it may also be 
distinguished from that species by its gelatinous nature. According to a 
note by Moore on a specimen from the Antrim coast preserved in the 
Herbarium of the Royal Botanic Gardens, Kew, the arrangement of the 
siphons is frequently spiral in this species. Material obtained from Torquay 
‘in April 1920 exhibited this phenomenon, the amount of twist being about 
equal to that which is typical for P. atro-rubescens. 
Habitat. On rocks, stones, and shells at extreme low-water mark. Frequent. 
British Records. Scotland, Northumberland, Kent, Sussex, Hants, Dorset, 
Devon, Cornwall, Hilbre Island, Wales, Isle of Man, Ireland, and the 
Channel Islands. 
Distribution in Europe, Atlantic shores of Europe. 
4. P. FIBRILLOSA Grev. in Smith’s Engl. Flora, v. 1833, p. 334. 
HHutchinsia fibrillosa C. A. Ag. Sp. Alg. vol. ii. 1828, p. 78. 
H. lubrica C. A. Ag. Le. p. 94. 
P. lasiotricha Kütz. Tab. Phye. xiii. 1863, p. 23, tab. 72 (e-h). 
References. Agardh (2) n. p. 991; De Toni (22) p. 919; Hauck (81) 
p. 230. 
Icones. Harvey, Phye. Brit. pl. 302. syn. 117. Kiitzing, Tab. Phyc. 
xii. ec. Exsiceate. Crouan, Alg. mar. Finist. no. 296, 1852. Lloyd, Alg. 
Ouest Fr. no. 136, 1854. Wyatt, Alg. Damnon. no. 136. 
DrsoniPrioN.— Habit. Plants solitary, as much as 15 ems. in length. 
Branehing alternate, lowest ones longer than ihe upper, giving conical 
appearance. Branches clothed with numerous ramuli; substance cartila- 
ginous except in the smaller branches and ramuli, where it is gelatinous: 
Siphons. 4 primary pericentral, with which the four secondary alternate 
on the outside, the diameter of the central one being about l the radius 
of the filament. A band of corticating cells present at the base. Colour. 
Brownish or straw-coloured when growing in sunny pools, darker in deeper 
water. Anatomy. Articulations obscured in the lower parts of the plant ; 
from 13 to twice as long as broad in the smaller branches and 
ramuli, the tips of the latter being clothed during summer with multi- 
cellular dichotomous. hairs. Attachment organ. Plant attached by an 
expanded dise of the same type as P. elongata. Length of the rhizoids very 
variable when the plant is epiphytic, e. y. on Rytiphlea pinastroides Ag., the 
outer ones being longer and enabling the attachment dise to grasp the 
thallus of the host. Reproductive organs. Tetraspores intercalary in develop- 
ment in swollen ramuli. Antheridia borne on filamentous hairs at the apices 
