2 BOTANICAL MICROTECHNIQUE. 



7. Amido-compounds. 



128. -The amido-compounds (amido-acids and acid amides) 

 are characterized by the fact that they contain the uni- 

 valent radical NH 2 . They are therefore nitrogenous, and 

 very probably play a most important role in the formation 

 and transference of the albuminous materials. We have, 

 however, trustworthy microchemical methods for recogniz- 

 ing only two of the amido-compounds of the fat group, 

 leucin and asp ar agin ; while of the aromatic amido-com- 

 pounds tyrosin may be mentioned here (cf. 134). 



a. Leucin, Amido-caproic Acid, C 5 H 10 NH 2 .COOH. 



129. Leucin was microchemically recognized by Borodin 

 (IV) in the leaves of etiolated specimens of Paspalnm elcgans 

 and DaJilia variabilis. He made yse for this purpose of its 

 property of subliming without decomposition when care- 

 fully heated to 170 C. Dried sections were covered on the 

 slide with a clean cover-glass and carefully heated. When 

 leucin was present, tiny, crystalline, doubly refractive scales 

 of this compound were deposited on the under side of the 

 cover-glass, under this treatment. These could then be 

 tested with a saturated aqueous solution of leucin (cf. 

 71, note). 



Leucin is also deposited in crystalline form, as are aspara- 

 gin and tyrosin, if sections containing it are treated with 

 alcohol and allowed to dry slowly under a cover-glass.* 



b. Asparagin, Amide of A spar tic {Amidosuccinic) Acid, 

 C 2 H 3 NH 2 .CONH 2 .COOH. 



130. Asparagin is soluble in water and occurs only in 

 solution, in vegetable cells. For the recognition of aspar- 

 agin according to the method first used by Borodin (II), the 

 sections are treated with absolute alcohol under a cover- 



* Leucin has recently been recognized by Belzung (II) in the seedlings of 

 Lupinus albus. It is here precipitated in the tissues preserved in glycerine 

 in the form of heart-shaped lamellae, which are often aggregated into 

 sphaerocrystals. 



