IOI2 The American Naturalist. [November, 
man's hand. It much resembles in appearance floating particles of 
decaying flesh, in this respect being similar to Chlamydococcus pluvialis 
A. Br., from which it is with difficulty distinguished without the aid 
of a microscope. (The latter I collected in quantity in a pond in 
Wessington Hills, Dakota, last April. The color is a somewhat deeper 
violet purple.) This interesting little plant has not been found before 
in America, so far as known. It is distinguished from known Ameri- 
can species by its smaller size and violet color. Rev. Francis Wolle 
has examined specimens of it and confirmed my identification. I have 
to thank him also for much aid in my study of Algae. 
Chroococcus cohcerens Naeg. A beautiful blue-green species. 
Common. 
NOSTOCACE^. 
Oscillaria. Several species were observed. 
Nostoc pruniforme Ag. Very common, forming olive or dark brown, 
nearly regular balls, from one millimeter diameter to the size of a 
plum. Floating in every pond. 
ALMELLACE^. 
ally of 1 
Scenedesmus ditnorphus Kg. Not common. 
Scenedesmus obtusus Meyen. Very common, presenting a number of 
Pediastrum angulosum (Ehr.) Menegh. Common. Cells about i6 
/i in diameter. 
Pediastrum borganum (Turpin.) Menegh. Common in several stages 
of development. Empty colonies occur frequently, the zoogonidia 
having escaped from all the cells. 
Raphidiiim polymorphuni Fres. One specimen was observed in the 
examination of the material, belonging probably to the variety sigmoi- 
deum Rab. 
Polyedrium trigonum Ngeg., \ax.punetatum Kirch. Several specimens 
that I take to be this variety were found. 
Protococciis viridis Ag. A deep green aquatic variety is quite common. 
Euglena viridis (Schrank.) Ehrenb. 
DESMIDIACE,«. 
We are usually told that desmids are to be sought in fresh, pure 
water only. My experience in Nebraska has not confirmed this state- 
ment. I have frequently searched running waters and springs for 
