128 BOTANICAL MICROTECHNIQUE. 



ined are directly placed. The parts containing veratrine 

 then become first yellow, then reddish orange, and finally 

 red-violet. 



/. Xanthine, C 5 H 4 N 4 O 2 . 



2223.. Xanthine has been recognized by Belzung (II, 49} 

 in considerable quantity in the seedlings of Cicer arietinum. 

 It crystallizes out in the interior of the cells of plants placed 

 in glycerine. 



ii. Nitrogenous Bases. 



Nicotine, C 10 H 14 N a . 



223. The following reactions have been recommended for 

 the recognition of nicotine by Errera, Maistriau and Clau- 

 triau (I) : PJiospho-tungstic acid gives a heavy precipitate, at 

 first yellow, then yellowish green ; mercuric chloride, a white 

 one, soluble in an excess of ammonium chloride with heat ; 

 potassic-mercuric iodide, an abundant white one ; platinum 

 cJiloride, a yellowish-white one, soluble at 70 C. ; iodine and 

 potassium iodide, a brownish-yellow one which disappears 

 later. 



12. The Proteids and Related Compounds. 



224. Although the albuminoid substances or proteids 

 undoubtedly belong to the most important constituents of 

 the plasma-body of the cell, we still know very little of their 

 chemical constitution. But, at all events, we have here to 

 do with a group of dissimilar compounds, and already various 

 investigators have distinguished a large number of different 

 proteids. But since no classification of the proteids has yet 

 found general acceptance, and especially since the exact 

 microchemical distinction of the proteids which are recog- 

 nized macrochemically is not yet possible, it seems best not 

 to discuss these researches here ; and so much the more so 

 since they have not led to any morphologically or physio- 

 logically interesting results, so far as concerns the vegetable 

 organism. But it seems important to briefly collate the 



