286 DR. LILY BATTEN ON 
2, P. macrocarpa Harv, in Mackay’s “Flora Hibernica,” iii. 1836, p. 206. 
P. pulvinata Harv. Phye. Brit. pl. 102. p, syn. 108 (excl. syn.). 
P. sertularioides Holmes & Batters, Rev. List, 1892, p. 94. 
References. Agardh (2) ii. p.969 ; Batters (9) p. 79: Cotton (16) p. 138; 
De Toni (22) iv. p. 870; Hauck (31) p. 219. 
Icones. Harvey, Phye. Brit. l.e. Hwsiccate. Crouan, Alg. mar. Finist. 
no. 288 (excl. syn.), 1852. Wyatt, Alg. Damnon. no. 215. 
Description. —Habit. Occurring in roundish tufts, rarely more than an 
inch in height. Main branches showing marked tendency to pseudo- 
dichotomy, ramuli unilateral or alternate, generally backwardly directed. 
Siphons. 4 pericentral and small central. Colour. Dark reddish-brown. 
Anatomy. Length of articulations variable, 3-4 times as long as broad in the 
main branches, 2-3 times their breadth in the smaller branches, frequently 
not more than half their breadth in the ramuli. Attachment organ. Young 
plant attached to substratum by two rhizoids formed by longitudinal prolifer- 
ation of pericentral siphons. Later, the siphons of procumbent branches 
form numerous rhizoids, each bearing a well-developed disc. The latter 
encircle angular fragments when the plant grows on a sandy substratum. 
Reproductive organs. Tetraspores borne in the ramuli, intercalary in develop- 
ment. Cystocarps stalked, urn-shaped, elongated at the apex with a con- 
tracted ostiole, very large in proportion to the diameter of the filament. 
P. macrocarpa was wrongly united with Autchinsia pulvinata Ag. and 
Conferva pulvinata Roth, Cat. ex Phye. Brit. (28. p. 120), but rightly 
presented by Batters (9. p. 79). Bornet (11. p. 306) suggests that P. macro- 
carpa is a form of P. sertularioides, although he has kept them apart. 
Hutehinsia pulvinata Ag. has six pericentral siphons, and has been separated 
by Areschoug as P. hemispherica (11. p. 306). 
Habitat. Occurring on rocks between the tide-levels and creeping in the 
sand. Common. i 
British Records. North Ronaldsay, Berwick, Cullercoats, Brighton, Isle of 
Wight, Studland, Swanage, Portland, Torbay, Plymouth, Fowey, Falmouth, 
Sennen Cove, Mount’s Bay, Padstow, Ilfracombe, Anglesea, Hilbre Island, 
Ardrossan, Saltcoats, Bute, Port Stewart, Balbriggan, Miltown Malhay, 
and the Channel Islands. 
Distribution in Europe. Atlantic and Mediterranean coasts. 
3. P. RauNENSIS Thuret, Etudes Phyc. 1878, p. 84. 
Reference. Oltmanns (45) i. p. 600 et seq. 
Icones. Thuret & Bornet, Études Phye. 1878, pl. 41. Oltmanns, Morph. 
und Biol. der Algen, 1904, fig. 377. 
DESCRIPTION.— Habit. Occurring in tufts, 8-10 cms. in length, branched 
from the base. Branches arising alternately, upper parts being clothed with 
