S03IE SPECIAL METHODS 641 



Caldwell {Ann. Bot. xxxix, 1925, p. 212) cuts off the leaf at 

 the middle of the petiole and inserts the cut end in the lower end 

 of a glass tube which is then filled with the stain. The plant is 

 then placed in conditions favourable for transpiration. 



Gourley's Basic Fuchsin Method {Stain Tech., v, 1930, p. 99). 

 Remove the plants from the soil, wash the roots and immerse 

 them for twenty-four to forty-eight hours in a basic fuchsin 

 solution prepared by dissolving 50 mgm. of the dye in 2 c.c. 

 95 per cent, alcohol and diluting with 100 c.c. tap-water. After 

 removal from the dye, wash in water and (1) dissect under a 

 binocular microscope after boiling in water or very dilute caustic 

 potash solution. Or, (2) clear by running through the alcohols 

 and then mixtures of alcohol and xylol into j)ure xylol ; this 

 requires ten to twelve hours. 



Camp axd Liming {Stain. Tech., vii, 1932, p. 91) immerse the 

 cut ends of living plants in a slightly alkaline aqueous solution of 

 basic fuchsin. When the dye has appeared in the parts desired, 

 examine by sectioning, etc. Permanent mounts may be prepared. 



Taylor immerses cut ends of vascular plants in eosin solution. 

 If the plant is sufficiently tender, plunge the entire stained shoot 

 in 2 per cent, acetic acid in absolute alcohol to fix the stain and 

 dehydrate the tissues. After a few hours clear in synthetic oil of 

 wintergreen. 



1269. Microincineration (see § 678). A thin section of plant 

 tissue carefully heated to destroy the organic matter leaves the 

 ash in its original position and sometimes unaltered. Such an 

 outline of the plant asli constituents is called a spodogram. If the 

 heating is continued only long enough to carbonise the tissue, the 

 result is called an anthracogram . 



During the carbonisation of plant sections protected with a 

 cover-glass, the colour of the tissue changes from yellow to red, 

 brown, and finally black. By heating only to the red-brown stage, 

 the material is in the best condition for photomicrography. The 

 distribution of minerals in single cells, as well as in whole tissues, 

 can be presented with a fair degree of accuracy. Silica alone is 

 unaltered by incineration. When alkaline salts are present as 

 well, heating causes the silica to melt and change its form. 

 Remove the alkalies with mineral acids, wash in water and then 

 incinerate. Calcium salts, usually the oxalate, are changed to the 

 carbonate without altering the form of the original crystals. 



All kinds of plant material may be used, either fresh or dried. 

 Thick leaves must be sectioned, 20 to 30/Lt giving the best results. 

 Wood contains relatively few crystals and must be cut thicker. 

 Bark and cortex are commonly crammed with crystals and need 

 to be cut very thinly. The epidermis, usually silicified, is best 

 used alone. Thin sections of coal may be treated similarly. In 

 the best methods, sections on a slide are placed inside a quartz 



VADE-MECUM. 21 



