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SELECTED ARTICLES. 
In the last peculiarity this substance resembles the opaline 
matter, which, however, is in every respect chemically differ- 
ent from it. M. Nees d'Esenbeck proposes for it the name 
saprocyanine, or rather as the colour appears blue and red, 
that of saprochrome. 
As it is to be presumed that the source of the colour exists 
in the confervas which belong to the genus oscillaria, the fol- 
lowing comparative experiments were made: 
A liquid containing vegetable albumen and prepared with 
the juice of the potato, was placed in the same circumstances, 
but without obtaining the result expected. With the zygne- 
ma quininum, the sphxrococcus crispus and the pamella 
cruenta of Agardh, the same thing occurred. The addition 
of muriatic acid did not produce a blue colur. 
The recent nostoc communis exhibited at the end of twelve 
days a red tint, without this alga being altered, but the colour 
did not continue long. The dried nostoc produced no colour 
at all. 
The experiments with the oscillaria nigra (Agardh,) were 
more successful. This oscillaria submitted to experiment on 
the 28th of January, exhibited in four weeks upon the surface 
of the deposit a beautiful shade of colour between violet and 
red, which upon agitation was communicated to the water. 
The liquor at that time exhaled a strong marshy odour, with- 
out the cadaverous character belonging to the phenomenon 
produced by the oscillaria from Aix la Chapelle. 
The cercaria viridis M. which in the summer of 1835 had 
collected in considerable quantity in a reservoir of the botanic 
garden, so that the entire surface was covered with a thick 
grass green layer of dead animalcules, did not produce the 
colour in question. 
It cannot be any longer doubted that the very remarkable 
genus oscillaria more particularly, and the nostoc communis, 
both equally abounding in azote, were the causes of the phe- 
nomena we have described; and that azote which distinguishes 
these genera from the various other common confervae must 
