148 PREPARATION OF OBJECTS FOR THE MICROSCOPE. 



thoroughly washed in several waters to remove all trace of the 

 cry stall izable solution. 



Now in order to bring out and to contrast the various tissues, 

 as the woody fiber, the cell walls, the ducts and spiral vessels, it 

 is necessary to recolor these objects ; and it is highly desirable, if 

 possible, to color the various parts differently. Now it is a sing- 

 ular and fortunate fact that certain colors, or at least certain 

 pigments, will either go to certain sets of tissues and leave the 

 others entirely unaffected, or they will color certain tissues 

 quicker and more readily than they will others. Thus carmine 

 dissolved in water with a few drops of aqua-ammonia in it, will 

 color only cell contents. Therefore, for carmine to have its best 

 effect, or indeed any great effect, it is necessary that the leaves 

 or thin sections be decolorized in alcohol, which does not remove 

 the albuminoid matter. Again, the extract of logwood, dissolved 

 in weak alum water, will color first the woody cells or fibers, 

 then other cell walls, as the pith and leaf cells ; and finally, if 

 the specimen is left in it long enough, it will color the spiral and 

 other vascular tissues. It is therefore well to remove the objects 

 from this dye before its work is complete say in from fifteen 

 to thirty minutes. And if it has then colored them too far or 

 too deeply, they -may be soaked in pure alum water, which will 

 remove the color in the reverse order already named above. 

 Lastly, aniline blue dissolved in alcohol will color spiral tissues, 

 hairs, glands, resin dots, leaf veins and generally all that is left 

 uncolored by the other pigments. I have not however been able 

 to color the stellate hairs of Deutzia, Croton, Shepherdia and 

 others, with aniline blue. Aniline green will color them ; but it 

 is not always a permanent color. It is very powerful in its action 

 and requires only a minute or two to do its work. 



A general formula for double or multiple staining may then 

 be given as follows : Carmine one day, logwood half an hour, 

 and aniline blue an hour. But it is nevertheless true that each 

 kind of objects, as for instance sections of stems, thick leaves 

 and thin leaves, leaves to show crystals, and those to show hairs 

 or glands, will require a somewhat different treatment one from 

 the other. It is very desirable that experimenters in this field 



