52 
NEW OR CRITICAL BRITISH ALGAS. 
attenuated above, 9-20 p in diameter. Joints from twice to 
four times shorter than the diameter of the filament. Apical cell 
rounded. Calyptra absent. 
In shallow pools near high water mark. Weymouth. 
(E. A. B.) 
Dr 0. Norstedt has kindly furnished us with the following list 
of Algas found by him during his stay in Great Britain : — 
Phormidium minutum , Gom. ; Oscillatoria unqinata , Ag., et 
Oscillatoria limosa , Ag. Penzance, in running water near Hey 
Moor, May 30, 1885. 
Phormidium uncinatum , Gom. ; Ballachulish, July 18, 1885. 
Phormidium autumnale , Gom. ; near Penzance, June 1, 1885. 
Phorm. Retzii, Gom. non Kiitz. Torrent Walk, near Dolgelly, 
June 25, 1885. 
Oscillatoria limosa , Ag. non. Kiitz. (0. Frcelichii , Kiitz.) 
Esher, May 9, 1885. 
Symploca muralis , Kiitz. Between Penzance and Hey Moor, 
May 30, 1885. 
Symploca muscorum , Gom. ; Cirencester. (Legit. W. Joshua). 
Bibliography. 
Monographic des oscillariees (Nostocacees homocystees). Par M. 
Maurice Gomont. 
The completion of M. Gomont’s invaluable Monograph of the 
Oscillariacecc marks an epoch in the history of this interesting, 
but neglected, group of algas. Few and ill-defined as are the 
characters which can be utilised for classifying the other groups of 
the NostochacecBy they are more and better marked than those which 
can be used in grouping the Oscillariacece. In this group neither 
hair, heterocysts, nor chromatophores are to be found, and the 
presence of nuclei has never been clearly demonstrated. M. 
Gomont has consequently taken the nature of the sheath — an 
organ hitherto very imperfectly understood — and the compara- 
tive number of the trichomata enclosed in it as the basis of his 
classification. 
He divides the Homocystece into two great tribes, the Vaginariece , 
in which, with the single exception of Porphyrosiphon, two or 
more trichomata are contained in a common sheath, which is, in 
most species, tinged with a brownish, red, or blue colour, and the 
Lyngbyece, in which a single trichoma is contained in each sheath, 
which is very seldom tinged with brown, never with red or blue. 
The Vaginarece are then divided into two sections, in the first of 
which few loosely packed trichomata are present in each sheath, 
which in most species is coloured. This section contains four 
genera — Schizothrix with 27 species, Porphyrosiphon one species, 
Hydrocoleum 10 species, and Dasyglcea with a 'single species. The 
second section contains genera in which very numerous closely- 
