422 Wisconsin Academy of Sciences , Arts, and Letters. 
A MONOGRAPH OF THE ALGAL GENUS 
SCENEDESMUS BASED UPON PURE 
CULTURE STUDIES 
Gilbert Morgan Smith 
The species that have been described in the genus Scened- 
esmus are based almost wholly on field material. The specific 
differences are founded on the shape of the cells, presence 
of horns, teeth, lateral ridges, and cell measurements. The 
question of the amount of variation within the limits of a 
single species, however, has always been one of consider¬ 
able dispute, since there has been no way of determining 
whether or not any particular character is permanent 
or persists for a single generation only. The application of 
the pure culture method to the study of algae by Beyerinck 
in 1891 has given an exact method for the study of variation 
within the limits of a single species. Methods for the isola¬ 
tion of algae have been described by Beyerinck, Chodat, 
Grintzesco, and myself, so that an extended account of the 
process is superfluous. 
In this article an attempt is made to cover the entire 
literature relating to Scenedesmus for the purpose of deter¬ 
mining the geographical range of the various species. For 
the sake of brevity in citation, articles are referred to by 
date only, and the letters A, B, C, etc. used to distinguish 
between the publications of one man for the same year. 
Exsiccatae have not been included since there were not 
a sufficient number available to warrant doing so. Geo¬ 
graphical distribution has been cited according to political 
rather than physiographical boundaries. In spite of the 
fact that these units of area are artificial and of unequal 
size this method is the most serviceable since geographical 
interest is generally confined to certain specific countries. 
