NEW OR CRITICAL BRITISH ALGE. 53 
packed trichomata are present in each sheath, which is always 
clearly defined and hyaline, never lamellose. This section contains 
but two genera, Sirocoleum with two species, and Microcoleus with 
ten. 
The Lyngbyece are also divided into two sections, the first con- 
taining those species in which the trichomata are multicellular, the 
other those in which they are unicellular. 
The first of these sections containing those genera with multi- 
cellular trichomata is again divided into two sub-tribes — -the 
Lyngbyoidece , in which the filaments are simple or pseudo-branched, 
the sheath firm, in some species yellowish-brown, the apices of 
the trichomata constantly straight; and the Oscillarioidece, in 
which the filaments are always simple, the sheath thin, always 
hyaline, mucous, more or less diffluent, absent, or not detected in 
many pieces. Apices of the trichomata not infrequently carved. 
The Lyngbyoidece contains three genera, Plectonema with eight 
species, Symploca eleven species, and Lyngbya twenty-one species. 
The Oscillarioidece contains five genera, Phormidium with twenty- 
nine species, Trichodesmium three species, Borzia one species, 
Oscillatoria thirty-eight species, and Arthrospira three species. 
The second section of the Lyngbyece , containing those genera in 
which the trichomata are unicellular, consists of a single subtribe, 
Spirulinoidece with a single genus, Spirulina , which contains nine 
species. 
M. Gomont’s monograph is prefaced by an interesting and ex- 
haustive account of the group taken as a whole. Every species, a 
specimen of which M. Gomont has been able to examine, is des- 
cribed in detail, and at the end of each genus a list of the doubtful 
and excluded species is given. A glance at the list of those 
plants which were once considered as distinct species of Oscil- 
latoria, but which must now, according to M. Gomont, be rele- 
gated to the limbo of synonymy, will give some idea of the im- 
mense amount of labour entailed by a work of this sort. M. 
Gomont is most heartily to be congratulated on the completion 
of his invaluable work, which, besides forming the basis of all 
subsequent works on the subject, will, we may hope, fix the classi- 
fication of this interesting but intricate group, at least, for some 
years to come. 
The Norwegian Forms of Ceramium. By M. Foslie (reprinted 
from “ Det. Kgl. Norske Videnskabers Selskabs Skrifter.,” 
1893). 
M. Foslie gives us in a paper of some twenty pages, illustrated 
by three photographic plates, the results of his study of the 
Norwegian Ceramia. The paper is of especial interest to British 
algologists as all the species and most of the forms men- 
tioned by the author are to be met with in more or less abundance 
on our own shores. The author’s account of the Norwegian 
Ceramia is based on an examination of the collections, now pre- 
