20 INTRODUCTION. 



in the sluggish current, or resting like a green skum on the surface, 

 they are readily seen and as easily gathered. No collecting tools are 

 demanded for either Algae or Desmids, except a dipper of some 

 kind, a common tin dipper is as good as anything, and a few bottles 

 or other vessels to carry the treasures home, and to keep them con- 

 cealed from inquisitive people; the collecting naturalist must always 

 be prepared for a meeting with such persons. 



Many media have been recommended for the preservation of these 

 beautiful plants. The trouble with the majority of these prepara- 

 tions is that they will in time, some usually in a very short time, 

 allow the cell contents to contract and to become so distorted that 

 the object is worthless for any serious study, and worthless, too, as 

 the object of beauty that it was when first mounted. Some of the 

 commended media act well on some kinds of Algae and Desmids, but 

 fail on others. The following are among the best, yet even these are 

 not all adapted to all the different kinds. They are mentioned in 

 the order of their excellence. 



CAMPHOR WATER. This is made by placing a lump of camphor 

 in distilled water and leaving it there for several days. Mr. W. H. 

 Walmsley, an expert preparer of microscopical slides, says that he 

 has had a specimen of Draparnaldia in camphor water for twenty 

 years, and that it is now as beautifully green as when first mounted, 

 and that the chlorophvll, its green coloring matter, seems to be un- 

 changed. When he desires to mount an Alga or a Desmid, he places 

 it in a small quantity of camphor water to which a few drops of glyc- 

 erine have been added. At first the plant will become lemon color, 

 but after a few hours the original green returns in all its vividness, 

 and then he at once mounts the plant in some of the fluid. 



CARBOLIC ACID WATER, made by adding a few drops of the acid 

 to a phial of water, is recommended by the Rev. Mr. Wolle, but he 

 says that although this will preserve them for months or even years 

 without deterioration, it may allow the coloring matter, the chlor- 

 ophyll, to fade; this however in the case of the Desmids is of little 

 importance. 



A SOLUTION OF CHLORAL HYDRATE, in the proportion of five 

 grains of the salt to one ounce of water, answers well for some 

 specimens. Like camphor water it has the merit of being easily 

 made and easily used. 



A SOLUTION OF COPPER made after the following receipt is admir- 

 able for some of the Algae, preserving the color and the form entirely 

 unchanged, while on others it will not act so favorably. 



