CELL-CONTENTS AND FORMS OF CELLS. i6i 



alkaloids form crystallizable salts and, in many instances, definite 

 double compounds. Nevertheless, not a great amount of progress 

 has been made in their detection and localization, either in the 

 living plant or in economic products. The reason for this is that 

 other substances, as calcium oxalate, may interfere with the 

 reactions forming crystals with the reagents, so that nothing 

 definite can be deduced. Then again, when an alkaloid is charac- 

 terized by certain color reactions, especially if a rose or violet 

 color is formed, it may be due to the reaction of the reagent with 

 carbohydrates or protein substance. For this reason practically 





Pig. 94A. Crystals of Piperine: A, cells of endosperm showing a single oil cell (b) in 

 which crystals of piperine have separated; (a) starch bearing parenchyma. B, piperine 

 crystals separated from sections which have been first treated with alcohol, and to the oily 

 globules remaining after evaporating the alcohol, a drop of distilled water has been added. 

 In from fifteen to thirty minutes there separate needles, short rods and aggregates of 

 piperine. — After Molisch's work on Histochemie. 



there are only a few instances where satisfactory results are 

 obtained in the study of alkaloids in plant tissues. These, for the 

 most part, have been obtained in connection with the dried mate- 

 rials of commerce. As it is very important that these studies 

 should be carried further, a few illustrations may be given. 



Hydrastis contains two alkaloids in considerable quantities 

 which form definite salts with nitric and sulphuric acids. Fur- 

 thermore, this plant does not contain calcium oxalate, so that the 

 crystals formed upon the addition of mineral acids could not be of 

 either the nitrate or sulphate of calcium, and if in other respects 

 they corresponded to the sulphates and nitrates of the alkaloids 

 peculiar to hydrastis, then the crystals must be salts of the alka- 

 Toids. If sections of the fresh rhizome of hydrastis or the moist- 



II 



