VARIATION IN THE DESMIDIE EF. 373 
one would conclude that the natural production of a permanent 
variation in a Desmid-species is a more difficult matter than at 
first imagined. 
Notwithstanding the interesting nature of this subject, only 
two short papers have appeared treating directly upon the 
variability of the Desmidiex. The first paper is by W. Schmidle *, 
in which, after a consideration of the variability of the granules 
ornamenting Cosmarium punctatum, Breb., and its allies, he 
formulates the following statements:—'*(1) Die Chlorophyll- 
struktur ist konstant bei einer Species dieselbe. (2) Die Gestalt 
der Zelle variirt innerhalb enger Grenzen. (3) Die Scheitel- 
ansicht zeigt konstant dasselbe Aussehen. (4) Die Granulation 
ist relativ sehr variabel. Doch ist eine gewisse Gesetzmüssigkeit 
iu der Anordnung der Punkte immer vorbanden, so Jedoch, dass 
dadurch noch sehr heterogene Stellungen móglich sind." 
The second paper is by Borge t, and in it he remarks upon 
the variability of Closterium moniliferum, Ehrenb., Cosmarium 
sp. (=C. Meneghinii var. ?), and C. Botrytis, Menegh.: he also 
mentions cases of variability figured by De Wildemann in 
Euastrum crassum, by Elfving in Micrasterias sp. (= M pinnatifida 
forms), by Johnson in M. pinnatifida, and by Borge in Xanthidium 
cristatum. Concerning Borge's paper I need say no more, but 
the four conclusions arrived at by Schmidle require a little con- 
sideration. 
In the first place, with regard to the structure of the chloro- 
phyll it may be said that the recorded observations dealing with 
the variability of the cell-contents are so few as not to 
admit the formulation of any definite statement concerning it. 
A. short account of all that is at present known about the subject 
is given at p. 399. 
More evidence is forthcoming as to the variation in the 
form and symmetry of the cell, all of which tends to show that 
there is a variability of outline for each species within certain 
limits, these limits being very narrow and almost inappreciable 
in some but very wide in others. Schmidle's third. statement 
with regard to the “ Scheitelansicht " really comes under the 
* W., Schmidle,“ Ueber die individuelle Variabilität einer Cosmarienspecies,” 
Hedwigia, 1893, Heft 3, pp. 109-115. 
t O. Borge, “ Ueber die Variabilität der Desmidiaceen,” Ofvers, af K. Sv. 
Vet.-Akad. Fórh. 1896, no. 4, pp. 280-204. 
