SECTION THREE 



Technique: 



1. Paraffin sections are brought down to 70% alcohol; then 

 stained for twenty-four to forty-eight hours in Solution A (over- 

 staining is not possible). 



2. Rinse in water ; then stain ten to fifteen minutes in Solution 

 B. 



3. Rinse in water; then rinse for fifteen seconds in Solution C. 



4. Stain ten to twenty-five minutes, according to the material 

 and fixative, in Solution D. 



5. Rinse briefly in Solution E. 



6. Immerse for about three minutes in Solution F. 



7. Rinse in Solution G. 



8. Rinse in two changes of xylol ; then mount in balsam. 



Results: 



Dividing chromatin, red ; resting chromatin, purplish ; nucleoli, 

 red (occasionally violet); nucleoplasm, colourless or greenish; 

 lignified walls, bright red; cutinized cell walls, reddish purple; 

 suberized walls, red ; cellulose cell walls, greenish orange ; cyto- 

 plasm, bright orange ; middle lamellae, green ; starch grains, purple 

 with green or orange halos (the colour of the halps soon becomes 

 replaced by purple in some types of materials) ; plastids, purplish to 

 greenish; invading fungal mycelium, green; the callose portion 

 of the guard cells of the stromata bright red and the remainder 

 purple ; and Casparian strips, red ; the remainder of the cell wall 

 of the endodermis, yellow. 



In sections of roots for the origin of the lateral roots, the 

 cytoplasm of the latter should be stained green, with purplish 

 nuclei, while the cytoplasm elsewhere should be orange with 

 red nuclei. 



The combination is exceptionally good for sections of lichens, as 

 the algae are well differentiated, and also for Puccinia graminis 

 telia and Uredinia. 



From Plant Microtechnique, by D. A. Johansen, by courtesy of McGraw-Hill 

 Book Company, Inc., New York. 



T 263 



