242 THE CELL 



ready for use, or may be prepared by this recipe {Gage's Hematoxij- 

 Uu]: Distilled water 200 cc. and potash alum 7^ grams, boil together 

 for five minutes in glass dish or agate ware. Add enough boiled 

 water to bring the volume back to 200 cc. When cool add 4 grams 

 of chloral hydrate and nf gram of hematoxylin crystals which have 

 been dissolved in 20 cc. of ninety-five per cent alcohol. This is 

 quite permanent, and becomes of a deeper color after standing for 

 some time if left in a light place and frequently shaken. It stains 

 the tissues which bear protoplasm and cellulose walls, causing them 

 to stand out in contrast with the other tissues. 



Preparing and Keeping Laboratory Material. — In preparing material 

 for the experiments outlined in Part III., the pupil or teacher will 

 find it best to get much of the material during the growing season 

 and preserve it until the time for use. Soft material should be 

 dehydrated and hardened by placing it in about 40 per cent alcohol 

 for several hours to two days, according to its size, and then plac- 

 ing it in about 70 per cent for the same lensrth of time. It can then 

 be placed in 80 per cent alcohol, and is ready for use at any time. 

 When thus preserved, the tissues containing protoplasm are some- 

 times much shrunken. For this reason it is well to preserve some 

 of the material in a liquid containing a great deal of water. One of 

 the best liquids is a 2 per cent or 2% per cent solution of formalin. 

 This preserves material well but does not dehydrate it. Formalin 

 burns the flesh. 



Free-hand Cutting and Mounting. — To cut sections, the material 

 may often be held between pieces of pith or smooth cork in the 

 microtome or fingers. The material and sections should be kept wet 

 with alcohol during the time of cutting. 



The sections when cut should be wet in water, then stained 

 with hematoxylin for a few minutes; drain off the hematoxylin and 

 rinse with water; then use ninety-five per cent alcohol to extract 

 all the water from the stetions; then pour on clearer for a few 

 minutes. Put a drop of Canada balsam on the sections, and they 

 are ready for the thin cover glass. Mounts thus made are permanent. 



Some reasons for the steps in the process may be understood 

 from the fact that hematoxylin does not mix readily with alcohol, 

 and balsam does not mix with water nor with alcohol. Sections 

 mounted before they are freed from water become cloudy and 

 worthless. 



Fixing and Microtome Sectioning. — For the purpose of preparing 

 permanent miscroscopic sections of leaves, wood, or any other plant- 

 tissues, select typical specimens of the part desired and cut them 



