166 NATURAL HISTORY MISCELLANY. 
they are presented in such a state that the finest ii of their sili- 
ceous epidermis can be observed, and they are the same time held 
within a preservative substance which does not d of eai move- 
ment and consequent danger of fracture; the Desmidiæ and t amen- 
tous Algæ in general cannot be enia so,and several means d been 
devised to keep them, all of which have been to a certain extent unsat- 
isfactory. Besides there are some Diatomacesz which grow in chains, 
as the Fragillaria, the frustules of which are united by means of a sub- 
stance that will not bear the contact of acid necessary to remove the cell- 
contents; and again there are others, as the Gomphonema, which are 
attached to submerged substances by means of a flexible stalk called a 
stipe, which would dissolve under the same circumstances. Such Diato- 
maces have been generally merely placed in a cell formed of «ement or 
other suitable substance, and preserved in a preservative solution con- 
sisting either of pure distilled water, or water containing creosote, cam- 
phor, or other substance possessing antiseptic properties. And the 
plan has been followed with the filamentous Desmidie and other Alg®, 
or the same effect is brought about by the colored matter generally ac 
juriste gatherings of such organisms. 
Y en is essentially as follows: Supposing I have a gathe ering 
Heiss Pri for the most part of a filamentous Desmid, as Desmidium 
Swartzii, which is a common species around New York city at certain 
s of the year, I place a small quantity of it in a test tube, and pout 
ing manner. Those, however, who have not the NON doing S0; 
or do not desire to prepare their own solution, can use t old by the 
pothecaries under the name of *Labarraque's Solution - Mi uar of 
D " which is, however, rather weaker than it is best often to use. 
solution I make by adding to the water a large excess of the co 
chloride of lime of the shops, which is fresh and has not stood for 2 
time in an open vessel exposed to the air, by means of which much of it 
becomes decomposed and useless for this purpose. After stirring well, 
and then allowing such a mixture to stand for a short time, until all that 
will not dissolve falls to the bottom, I pour off the clear liquid and add to 
it a concentrated solution of carbonate of soda, the common “+ washing 
onde." uat 
This is my solution of chloride of soda. The Alga is now boiled for 3 
few minutes in the solution, but not so violently or for such a length. of 
time as to break up the filaments, and then well and thoroughly was! 
with pure filtered or distilled water. It can thereafter be preserved in 
weak spirits, or. what I have found still better, water to which 2 few 3m 

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