274 
THE SEAWEEDS 
Polysiphonia nigrita Sonder. 
J. Ag. Sp. Alg. ii., 1048 ; Harv. Nereis Australis, p. 51; De Toni Syll. 
Alg. IV., % 928. 
Frond very similar to P. cancellata, with very thick main stems, vaguely 
branching; branches elongate, erecto-patent, decomposite; ramuli stout, 
slightly curved, subulate, spinaeform, sparse. Articulate, eight-nine siphons, 
articulations very short. Drying jet black. Substance rigid. 
De Toni includes P. nigrita under P. cancellata Harvey, and they are 
undoubtedly very closely related. However, in South Australian specimens 
of typical P. cancellata, the siphons of the larger branches in particular, 
and also the smaller, are arranged in very regular transverse layers, while 
in typical P. nigrita they are very much more irregular, forming no definite 
transverse layers. The ramuli of P. nigrita are stouter, and the colour very 
much darker than in P. cancellata. In well developed specimens the ter- 
minal dichotomous fibres on the ramuli are well developed in P. canoellata, 
but almost absent in P. nigrita. Harvey also recorded eight or nine siphons 
in the main stem of P. nigrita and only seven in P. cancellata. South 
Australian specimens show normally seven large siphons, with an occasional 
small eighth, in both forms. The principal distinction seems to be in cell 
arrangement and colour, and a dozen or so specimens examined were not 
difficult to separate on these characteristics. A much larger series of 
specimens is required to determine the validity of these distinctions, but 
P. nigrita seems to be at least a distinct variety of P. cancellata , and they 
are, therefore, separated here. 
The following species has been recorded from Victoria, but De Toni’s 
description is almost useless. The group to which it belongs cannot be 
ascertained without examination of authentic specimens, and it is placed 
after Cancellatae (seven, eight or nine siphons) for convenience. 
Polysiphonia caespitula Sonder. 
Kfitz. Tab. Phyc. XIX (1864), p. 15, t. 43; De Toni Syll. Alg. IV., 960. 
Fronds ecorticate. Eight siphoned. 
Victoria (Wilson Promontory). 
IV. — ATRO-RUBESCENTES. 
Siphons 10-16 or more. Fronds bright red, drying darker, cylindrical, 
branching vague or pinnate. Ramuli irregular. 
Polysiphonia atricapilla J. Agardh. 
J. Ag. Sp. II., 3, p. 1054; De Toni Syll. Alg. IV., 934. 
Fronds to 15 cm. high, branching irregular, pinnate; intertwined with 
finer virgate ramuli, glabrous at base, articulate and ecorticate. Ramuli 
widely spread, almost horizontal, sublinear, attenuated, obtuse, the lower 
slightly rigid. Twelve siphoned, articulations all short. Tetrasporangia in 
slightly verrucose ramuli, sparse, prominent. 
South Australia (Lacepede Bay), Western Australia, 
