96 Botanical Microtechnique 



for similar subjects. Other synthetic stearates should be tried 

 (Johansen 1940, McLane 1951). 



Microchemical Tests 



One of the important advantages of sectioning fresh initreated 

 material is the avoidance of the chemical and physical alterations that 

 are undoubtedly produced by the processing necessary for embedding. 

 Although the protoplasm is probably changed by the handling 

 incident to sectioning and moiniting fresh material, the nonliving 

 constituents of cells and tissues probably are not markedly changed 

 chemically. This makes possible the use of microchemical tests that 

 reveal with more or less acciaacy the chemical nature of important 

 structures. Although the science of chemical microscopy is highly 

 developed, it occupies a minor place or is \irtually ignored in many 

 botanical curricula. However, certain chemical tests are generally 

 regarded as indispensable in even an elementary stud) and are 

 therefore included here. (Loomis and Shull, 1937.) 



Starch; Iodine-Potassium Iodide Test (IKI) 



Water 100 cc. 



Potassium iodide 1 g. 



Iodine 1 g. 



Place a drop of the reagent directly upon the specimen. Most starches give 

 a blue-black color. Waxy starch, found in some genetic stocks of maize, turns 

 yellow or brown. By using a very dilute solution of the reagent and impart- 

 ing only a trace of color to the starch, the laminations in the granules may 

 be observed with the microscope. When testing entire living cells such as 

 those of S})irogyra or leaves like those of Elodca. the aqueous reagent reacts 

 very slowly, and a reagent made with 70'/c alcohol shoukl l)e used. 



Sugars; Osazone Test 



Sohilioii A 



Cilv(erin (\\arm) 10 cc. 



PlKiiyllndra/iiK-iiydrochloride ... 1.0 g. 



Solution B 



(.l)(.eriii 10 cc. 



Sodium acetate h() g. 



Mix a drop ol each sohuion on a slide, float the sections in the mixture, 

 place the slide over the moiuh ol a wide-mouthed flask containing boiling 

 water, and heat for 10 to 15 niin. Glucose and fructose produce fascicles of 

 yellowisii needles: m;illose |)r()cluces fan-sha])ecl chisters of llaltened needles. 

 After .^0 to 60 niin. of heating, sucrose becomes hydroh/ecl and reacts to form 

 needles like those produced bv glucose. 



