1890.] MICKOSCOPICAL JOURNAL. 129 



The Prepanition ol'Microscoiucal Sections tVoiu Barks and Roots.* 



I]v M. J. COLK. 



Barks and roots that have been (h'ied ninst be cut into small pieces 

 and soaked in water for several hours ; this will cause the tissues to 

 swell up and regain, to a certain extent, their natural shape. They are 

 then to be transferred to methylated spirit or alcohol, which should 

 be changed every twenty-four hours until no color comes from the tis- 

 sue. They will then be ready for cutting into sections, or they may 

 remain until required. 



Fresh specimens should be cut into small pieces anil placed in spirit, 

 which should be changed as above until no color is given oft fiom the 

 tissue. The hardening will usually be complete in a week, or they 

 may remain for any length of time until required for cutting. 



Some barks will be found too hard to cut; they may be softened by 

 soaking for a time in liquor potassa ; then wash well in water until all 

 trace (if potash is removed. 



Section Cutting. — Fairh- good sections may be made liy hand with 

 an ordinary razor. Hold the piece of tissue in the left hand, keeping 

 the forefinger straight so that it may form a rest for the blade of the 

 razor to slide on. A good strong army razor answers very well. 

 Hold it firmly in the hand and keep the handle in a line with the blade 

 and draw it from the heel to the tip through the tissue toward yourself 

 Keep the blade well wetted with dilute spirit, and as the sections are 

 cut place them in a saucer of spirit of water. 



Section Cutting with a Microtome. — If really good sections are 

 required, a microtome of some kind should be employed. Screw the 

 microtome to a firm table, and with the tube supplied with the ma- 

 chine, punch out a cylinder of carrot to fit the well of the microtome. 

 Cut this in half longitudinally, and scoop out sufficient space in one 

 half to take the tissue to be cut. Put the other half of the carrot in its 

 place, and make sure that the tissue is held quite firmly, but it must 

 not be crushed. Now place the whole in the well of the microtome, 

 and commence to cut the sections with a strong razor or the section 

 knife that is supplied with the machine wdien desired. Keep the blade 

 of the knife well wetted with dilute spirit, and as the sectit)ns are cut 

 place them in a saucer of spirit of water. 



Bleaching. — Vegetable sections generally require bleaching before 

 they can be properly stained. A solution of chlorinated soda is usually 

 used. Soak the sections in distilled water to remove the alcohol. 

 Pour otl' the water and add a c[uantity of the bleaching solution, and 

 allow it to act for from three to twelve hours, or imtil all color has 

 disappeared from the sections ; then transfer to water-, which must be 

 changed several times until all trace of soda is removeil. 



Staining Sections. — The best staining fiuid for general pinposes is 

 logwood. Take two ounces of ground logwood chips, place them in 

 a calico bag and run w'ater through it imtil scarcely any color comes 

 away. Drain away as much water as possible, remove the logwood 

 from the bag and spread it in a thin layer on a tray to dry. Dissolve 

 2 drams of potash alum in 12 ounces of distilled water. Put the log- 



* Read at a meeting of the London Chemists' Assistants' Association. 



