Blackman and Tansley. 
A REVISION OF THE CLASSIFICATION OF 
THE GREEN AL GJE 
BY 
F. F. Blackman, 
University Lecturer in Botany , Cambridge. 
AND 
A. G. Tansley, 
Assistant Professor of Botany , University College , London, 
{continued from page 168.) 
Fam. I. Archidesmidiaceae. 
Cells cylindrical, elongated, chromatophores various, with no definite 
planes of symmetry, constituent cells, united end to end in filaments, 
which break up before conjugation takes place. 
[It seems most natural to separate the two following genera from 
the rest, since they are clearly far less specialised. They strongly resemble 
Mougeotia and Spirogyra among the Zygnemoideae, and very probably 
stand close to the common ancestors of these and the Eudcsmidiaccce .] 
Genera. 
1. Gonatozygon. De Bary, 1858 . 
Chromatophore single, axile, band-shaped, bearing a 
single row of pyrenoids. Cell-wall covered with 
minute warts. 
2 . Genicularia. De Bary, 1858 . 
Chi omatophores several, parietal spirally-wound bands, 
each with a single row of pyrenoids. 
Fam. II. Eudesmidiaceae. 
Cells free or connected by their ends into threads, sometimes 
polysymmetrical and cylindrical or spindle-shaped, but usually 
symmetrical about only three planes at right angles to one another. 
Sub-Family. I. Peniete. 
Cells free, typically cylindrical or spindle-shaped, straight 
(rarely curved), usually without equatorial constriction. 
Genera. 
1 . Cylindrocystis. De Bary, 1858 . 
Cells cylindrical or oval, straight with rounded ends. 
Chromatophores two, one at each end of the cell, 
each consisting of a rounded body, containing a 
single pyrenoid, and numerous diverging rays. 
2 . Mesotcenium. Nageli, 1849 . 
Cell-form as in Cylindrocystis. Chromatophore con¬ 
sisting of an axile plate with one pyrenoid. 
