76 BULLETIN OF THE BUSSEY INSTITUTION. 
the plant which is supposed to be a nostoc. Undoubtedly, the most 
disagreeable odor ever found in fresh water may be produced by 
nostocs, using that word to designate the order Nostochinee ; but by 
no means all of the disagreeable odors and tastes arise from that source. 
To return to the cucumber taste, there is not the slightest proof that 
it is caused by any alge, either living or decaying. The water from 
the Bradley Basin showed no nostocs whatever, and no alge of any 
kind not also found in waters which did not have the cucumber taste. 
During the past summer, we have made experiments to ascertain the 
taste produced by different species of alge. For this purpose different 
species of Desmidiee, Conferve, and Oscillari@, were allowed to 
stand several weeks in glass jars filled with pure water; but, in no in- 
stance, was any thing like a cucumber taste produced, nor, in fact, was 
any describable taste perceived. 
As far as smells are concerned, our knowledge is more complete. 
It is known that, when living, different species of nostoc may produce 
two different kinds of disagreeable odors: first, an indescribably 
suffocating odor, as in the case of several Lyngbye and Oseillarie ; 
and secondly, a sulphurous odor, as is given off by species of Deggiatoa. 
A still more disagreeable odor is given off by species of nostoc in 
decay, an odor resembling that of a pig-pen.or very strong horse- 
dung. Most persons who have in midsummer walked through the 
bogs so common in New England must have recognized the stifling 
odor given off by the bluish-green masses growing on the mud or in 
shallow water. ‘These are usually species of Osczllaria, composed of 
filaments made up of small cells in rows, the filaments capable of 
moving on one another, so that, when placed on any flat surface, they 
push out from one another, and spread over a larger area, or, if placed 
on the bottom of a tumbler, they crawl up the sides. The chemical 
nature of the stifling odor is not known. This peculiar stifling 
quality is not peculiar to nostocs, or even to fresh-water plants. It is 
marked in several marine plants, as Polysiphonia fastigiata, which 
forms blackish tufts on the larger rock-weed. 
The alge which exhale sulphurous odors belong to the genus Beg- 
giatoa, which resembles Oscillaria in consisting of filaments endowed 
with motion, but which differs in color, being whitish, the cells being 
full of opaque granules. They look to the naked eye like white 
films covering decaying alge and other plants. They are found on 
