STRYCHNINE — SUBERIN AND SUBERIZED WALLS 363 



hydrate and iodine dissolves the protoplasmic cell-contents 

 and stains included starch-grains purple. This reagent is par- 

 ticularly adapted to demonstrate the presence of starch in 

 chloroplasts or amyloplasts. The bleaching effect of the chloral 

 hydrate is so great that starch may be demonstrated in whole 

 leaves by the chloral hydrate and iodine reagent. For the 

 further treatment of starch with reagents, see in the preceding 

 chapter under Eau de Javelle, Calcium Nitrate, Diastase, 

 Methvl-violet, Silver Nitrate. For the structure of starch- 

 grains, see page 177. 



Strychnine, C21H22N2O2.— This alkaloid occurs associated 

 with brucine in the seeds of Strychnos nux vomica, S. multi- 

 flora, and S. Malaccensis. When sections containing strych- 

 nine are treated with a solution of i gm. of ammonium vana- 

 date in 100 c.c. of sulphuric acid, they quickly take on a violet-red 

 color, which after a time changes to brown. If sections of 

 the seeds of Strychnos nux vomica are treated with sulphuric 

 acid containing an excess of eerie sulphate, the walls of the 

 cells are colored a bluish-violet. The sections must have been 

 previously treated with petroleum ether and absolute alcohol 

 to remove the fatty oils, grape-sugar, and brucine. The reagent 

 should be applied immediately before the observation is to be 

 made. If sections are treated with concentrated sulphuric acid, 

 and crystals of potassium bichromate are then added, a violet 

 color is produced. 



Suberin and Suberized Walls. — Suberized walls are stained 

 green when treated for about an hour in the dark by a freshly- 

 prepared strong solution of chlorophyll. A cold concentrated 

 solution of potassium hydrate colors suberized walls yellow. 

 When the potassium hydrate is heated yellow drops and granular 

 masses are formed. When suberized walls are heated in a solu- 

 tion of potassium chlorate in nitric acid, they become changed 

 into droplets which melt between 30° and 40° C, and which 

 are soluble in hot chloroform, alcohol, ether, benzol, or dilute 

 potassium hydrate. At ordinary temperatures concentrated 

 chromic acid solutions have little effect on suberized walls. A 



