and Laboratory Methods. 1641 



water snails and water beetles, will usually grow with little or no attention. In 

 most cases the jars should be covered. 



Many of the specimens may be preserved in various preserving fluids, and 

 some may be dried. These will be found very convenient in case fresh material 

 cannot be obtained when desired. 



Microscopic plants may be preserved in water, in homeopathic vials, pro- 

 vided a drop of carbolic acid is added to each bottle of material. 



Plants like mosses, liverworts, fleshy fungi, stems, roots, rhizomes, etc., may 

 be preserved in 70 to sO per cent, alcohol. 



The ordinary filamentous algae are usually well preserved in Ripart and 

 Petit's solution. 



Myxomycetes in the fruiting stage, woody fungi, lichens, some liverworts, 

 and many other plants may be kept in a dry condition in ordinary paper boxes. 



Ripart and Petit's solution : 



Camphor water - - - . - - 75 c. c. 



Distilled water - - - - - 75 c. c. 



Crystalized acetic acid . . . l gram. 



Copper acetate - - . . . 0.3 gram. 



Copper chloride ----- 0.3 gram. 



To make the camphor water, dissolve four grams of camphor in eight c. c. of 

 alcohol. Distribute this on clean cotton and expose until nearly all of the alco- 

 hol is evaporated ; then place the cotton in a funnel and pour distilled water 

 through it until 500 c. c. of percolate are obtained. 



For preserving algae, take a two per cent, solution of formalin and add to it 

 from three to five per cent, of the above solution. 



General pharmaceutical rule for making any lower grade or percentage of 

 alcohol from any given grade or percentage. 



Take of the grade at hand as many volumes as the number of the per cent. 

 you wish to make ; then add to this enough volumes of pure water to make the 

 total number of volumes agree with the number of the per cent, at hand. 



For example, suppose you have 95 per cent, alcohol at hand and wish to 

 make 70 per cent, alcohol, take 70 c. c. of the 95 per cent, alcohol and add to 

 this 25 c. c. of pure water. This will give you 95 c. c. of 70 per cent, alcohol. 



The following suggestions are oftered especially for the benefit of laboratory 

 students, although most of the directions will also be useful to the amateur 

 microscopist working at home. 



The microscope must always be handled below the stage and never lifted by 

 any part above the stage, otherwise the fine adjustment may be injured. The 

 microscope is a very delicate instrument. It must not be inclined for general 

 work, as temporary mounts will not stay in the field unless the stage is horii^on- 

 tal. While working, the observer should keep the side of the microscope with 

 the coarse and fine adjustments toward him. The microscope is not to be moved 

 about to obtain the light. This can be obtained from almost any direction by 

 adjusting the mirror properly. Great care must be taken so as not to run the 

 objective down into the diaphragm or onto the cover-glass and slide. The lenses 

 of the microscope must not be touched with the fingers. They must be wiped 



