THE GENUS POLYSIPHONIA, 307 
P. atro-purpurea Moore in Harv. Man. ed. i. p. 89, appears to be a variety 
of P. nigrescens with a more slender habit and corymbose ramuli. A variety 
which was brighter and more purple in colour with greater delicacy of rami- 
fication was described by Carmichael (28. p. 115) as P. violacea. This no 
doubt accounts for the one-time confusion between two species which are so 
distinct anatomically. A form with 16 siphons and long articulations has 
been separated by Moore as P. afinisin Ord, Surv. Londonderry, App. p. 11, 
t. 7, and figured by Harvey (28) 1.303. The siphons are somewhat twisted, 
but the twisting is very slight and variable. The plant shows lax growth, 
and combines corymbose branching with unusually long articulations and 
about 16 siphons. P. dichocephala, figured by Kützing (37) xiii. pl. 55, 
appears to be the same plantas that which Harvey describes as P. afi nis Moore. 
Material dredged in Plymouth Sound showed the antherida of P. nigrescens 
growing directly on short stalks on the ramuli and not on dichotomising 
fibrille. Under these circumstances the multicellular axes of the antheridia 
frequently protruded from their tips. 
Habitat. Attached to larger algæ, and on rocks and stones between the 
tide-levels. Common. 
British Records. Common almost everywhere on the shores of the British 
Isles. Var. P. affinis Moore (=var. e. affinis J. Ag.) : Mouth of R. Deben, 
Ramsgate, Eastbourne, Torbay, Carnlough near Glenarm, Cushendall, and the 
Channel Islands. Rather rare. 
Distribution in Europe. Atlantic shores. 
5. P. VARIEGATA J. G. Ag. Ale. Medit. 1842, p. 129. 
Grammita Bonnem. in Journ. Phys. xciv. (1822) p. 186. 
G. denudata Crouan, in Desmaz. exs. no. 1208, 1842 (excl. syn.). 
P. leptura Kütz. Tab. Phye. xiii. 1863, p. 28, tab. 89 (fi). 
P. denudata (fide Hauck) Kütz. Tab. Phyc. xiii. 1863, p. 28, tab. 90. 
References. Agardh (2) ii. p. 1030; De Toni (22) iv. p. 922; Falkenberg 
(24) p. 119 et seg. ; Hauck (31) p. 236. 
Icones. Harvey, Phye. Brit. 1846-51, pl. 155. syn. 119. Kützing, Tab. 
Phye. Le. ` Thuret et Bornet, Études Phye. 1878, fig. 42. Exsiccata. 
Desmaz. exs. no. 1208, 1842 (excl. syn.). 
Description.—Habit. An annual, ezspitose, tufts attaining a length of 
25cms. Branching pseudo-dichotomous, widely divergent, main axis flexuose. 
Siphons. 6 pericentral, surrounded by a band of corticating cells in 
the lower parts of the plant. Colour. Purplish-brown, with frequently a 
greenish tint in the principal branches. Anatomy. Articulations shorter 
than their breadth near the base of the plant, twice as long as broad in the 
principal branches, gradually becoming shorter upwards. Attachment organ. 
Plants attached by a disc at the base of the main axis, subsequently 
strengthened by rhizoids formed from the siphons and corticating cells of 
