Bibliographical Notices. 281 



The Green Algse (Chlorospennce), which contain both freshwater 

 and marine species, are arranged according to the system proposed 

 by the author in his paper on the distribution of those Algse, pub- 

 lished in the 'Annals of Natural History' for November 1861. 



As these plants are very difficult to be distinguished, except in a 

 living state (the chief character often disappearing when they are 

 dry, and indeed often shortly after they are gathered), the author 

 has not attempted to give any diagnosis of the species, but has only 

 referred to the works in which the species or presumed species are 

 figured, preferring, where he can, figures that are taken from living 

 specimens. 



Dr. Gray has suggested some improvements in the arrangement 

 of the Algse. Thus he has proposed to separate the families of 

 Melanospermee used by Agardh and Harvey into three orders, 

 according to the structure of the frond ; thus — 



Order I. Scytophyces. Frond leathery or membranaceous, formed 



of compact cellular substance: containing — 1. Fucacece ; 2. La- 



minariaceee ; 3. Dictyotaceee ; 4. Sporochnaeece. 

 Order II. Trichophyces. Frond subarticulate, with a jointed 



axis, and furnished with tufts of pinnate, jointed (deciduous) 



threads. 5. Arthrocladiacece. 

 Order III. Arthrophyces. Frond formed of jointed filaments, 



which are either free or united into a compound body. 6. Chor- 



dariacece ; 7. Ectocarpacece. 



Iu the families he has characterized three new genera, viz., 



1. Fasciaria for Laminar ia fascia. 



2. Sphcerophorus for Ectocarpus granulosus and its allied species. 



3. Hincksia for Ectocarpus Hincksii. 



In the Rhodosperms he regards the anomalous genus Hapalidium 

 as the type of a family. It has been suggested that that genus may 

 be only the very young state of Melobesia ; but this theory wants 

 further examination, as the glassy texture, the form of the frond, 

 and cells are very unlike those of any species of the latter genus, 

 which is always calcareous and opake, and formed of several layers 

 of cells, even in its thinnest state of development. Again, if it is 

 the young state of that very common and universally spread genus, 

 why is it so seldom observed, when the Melobesice are to be seen on 

 almost every kind of marine body 1 



In the Chlorosperms, Dr. Gray has characterized the following 

 genera as new, viz. — 



Leptocystea for Cladophora pellucida. 

 Vagabunda for Cladophora fracta. 

 Cystothrix for Cladophora Rudolphiana. 

 Cystophora for Cladophora littorea. 

 Calonema for Callothrix mirabilis. 



The list of the Diatomacese seems to have been prepared by 

 Mr. Carruthers with great care ; and it will be very useful for the 

 collectors of that very numerous and intricate class of minute plants. 



