144 Methods in Plant Histology 



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The solutions A, B, and C keep well separately, but not when 



mixed. When wanted for immediate use, mix A, 1 . 8 c.c. (30 minims), 

 B, 3.7 c.c. (60 minims), and C, 1.8 c.c. (30 minims), and add 30 c.c. 

 (1 oz.) of water. 



A correctly exposed plate will develop in about 2J minutes, and 

 the tone should be a warm black. Brown tones are secured by 

 increasing the quantity of C, while A and B remain the same. 



Reducing Overexposed Negatives and Lantern Slides. In case 

 of overexposure, the negatives or lantern slides can be saved by 

 reducing. The reducing solution should be applied as soon as the 

 negative is well fixed in hypo. If a negative which has been washed 

 and dried is to be reduced, it should be soaked in water for half an 

 hour before using the reducing solution. 



The following is a good solution for most purposes: 



Metric Apothecaries 



/ Water 473 c.c. (16 oz.) 



' \ Hyposulphite of soda 31 g. (1 oz.) 



/ Water 473 c.c. (16 oz.) 



' \ Red prussiate of potassium 31 g. (1 oz.) 



Solution B must be protected from the light. Cover the bottle 

 with black paper and keep it in the dark when not in use. 



Mix only for immediate use 8 parts of A to 1 of B and use in rather 

 subdued light. A dark room is not necessary, but avoid bright light. 



When the negative or lantern slide becomes satisfactory, wash 

 it in water as thoroughly as if it had just come from the ordinary 

 hypo fixing solution. 



Intensifying Underexposed Negatives and Lantern Slides.- 

 Even if a negative or lantern slide has been considerably overexposed, 

 it can be reduced quite satisfactorily; if much underexposed, little 

 can be done for it; if only slightly underexposed, it may be greatly 

 improved by the following solution: 



Metric Apothecaries 



( Bichloride of mercury 2 g. ( 31 gr.) 



A | Water 100 c.c. ( 4 oz.) 



[ Bromide of potassium 2 g. (31 gr.) 



( Sulphite of soda crystals 10 g. (154 gr.) 



\ Water 100 c.c. ( 4 oz.) 



