1893.] THE MICROSCOPE. 2£ 



staining vegetable tissues. But in this condition it is too strong 

 for use ; dilute until the specimen may be seen when immersed, 

 and in a white dish. Give a???ple ti??ie for staining ; here is the 

 secret. 



" Take next, or first if you like, aniline blue, and mix in water ; 

 strength not important. Make a solution of picric acid in alco- 

 hol, add a few drops of the picric acid solution to the solution of 

 aniline blue until you develop a chlorophyl green ; now soak 

 in this liquid a few hours', or a day ; perhaps it will stain some 

 parts which haematoxylin will not — growing points, spores, 

 crystoleths, stomata, etc. It is sometimes best to stain first 

 in the green, then in the violet. Never allow your specimens 

 to dry, and absolute alcohol is not needed. Now immerse in 

 95 per cent, alcohol to dehydrate. Alcohol precipitates the 

 haematoxylin in the tissues, and extracts the excess of picric 

 acid, and fixes a beautiful blue-green color just where nature 

 likes it best, while the alum prevents structural change in the 

 most delicate parts. You may keep specimens for weeks in 

 this watery alcohol, and everv cell wall will become more dis- 

 tinct until you find time to mount. 



" Clarify the specimen in oil of cloves, thoroughlv drain off all 

 the superfluous oil of cloves (I lay the specimen on my hand ; 

 that soaks it up), then mount in Canada balsam." 



I do not know how thick a leaf must be to be too thick to 

 show clearly through the leaf the cells on the underside, but a 

 mullen ( Thapsus verbascum) will show each layer from the 

 hairs on the top to the tips of the hairs on the underside as 

 clearly as if the cells ivere made of spun glass. 



Staining Vegetable Sections.— Having cut thin sections of 

 any plant or stem, the specimen may be rendered more intelligi- 

 ble by staining it before mounting. Different dyes stain different 

 parts of the structure and so make these parts seem more promi- 

 nent. The contents of cells are also brought to view in this man- 

 ner. 



There are three kinds of effects produced by stains : (i) Some 

 stains attack the nuclei and are called nuclear stains. These leave 

 all but the nuclei uncolored. Haematoxylin and carmine are prom- 

 inent nuclear stains. (2) Some stains color the ground substance 

 and leave the nuclei uncolored. or color all the tissue uniformly. 

 These are called plasmatic stains. The contrasts produced by 

 coloring nuclei with carmine and the ground tissue with a stain, 

 such as eosin, is very striking. (3) Specific stains color certain 

 elements of the tissues only. For instance, liquefied tissues are 

 stained with methyl green. Cellulose may be colored blue. Lig- 

 nin may be colored yellow. 



From these principles result double and even triple staining of 

 the same specimens, but the process is tedious. 



