1 



of alcaloids in the cells is not too small no harm is caused 

 by tins, while it is very advantageous in as much as the 

 precipitate after this treatment becomes much less soluble 

 in glycérine. 



Sections so treated can subsequently be mounted and ex- 

 amined in glycérine which on account of the clearifying 

 properties of the glycérine is of no small advantage with 

 necessarily rather thick sections. 



If very little alcaloid be présent in the cells the mode 

 of proceeding just described, is unadvisable. In that case 

 it is much better to mount the section after being well 

 washed in water and subsequently cause a drop of the 

 stocksolution of iodine, put at the border of the cover- 

 slip, to diffuse into the mounting fluid. In this way ohh 

 can see the precipitate originate in the cells. With 

 bicarbonate of potassium aud such like reagents which 

 have a plasmolysing influence the same mode of procee- 

 ding is highly advisable. Bij means of them one first 

 observes the contraction of the vacuole and the cellsap is 

 seen as a clear globe. The reagent has not yet penetrated 

 through the wall of the vacuole; now it does and behold the 

 appearance of the precipitate as if the cell were touched 

 bij the sorcerer's rod. A fine instance of this has been 

 pictured in fig 64 PI III. (*) 



Wherever cells greatly stretched in longitudinal direc- 

 tion are met with another diffculty occurs. In those cases, 

 for example in the leafstalk, ail cells are opened by a 

 cross -section, the alcaloid escapes; or if one makes a 

 section with unopened cells it is so thick that nothing 

 can be distinguished. It is of course possible to examine 

 a longitudinal section of such an organ, but frequently 



(i) Wherever now and hereafter référence is made to figures and plates 

 the atlas of the Dutch text is meant, 



