458 THE ANATOMY OF WOODY PLANTS 



the strength of one-half of i per cent in distilled water. In some 

 instances this is too great a concentration and leads to overstaining. 

 This may be remedied by the transfer of the sections to distilled 

 water with a few drops of iron-alum solution in which bleaching 

 slowly takes place. When a sufficient degree of decoloration has 

 been attained, the sections must be washed in repeated changes 

 of distilled water as in the first procedure, otherwise the blue colora- 

 tion will fade in a short time. A better method is to stain more 

 gradually, using only a few drops of the solution of hematoxylin 

 described above. Slow staining in general gives better results 

 than rapid. The blue-tinted sections when properly colored are 

 transferred to distilled water and thence to distilled water to which 

 a drop or two of safranin has been added. This stain is prepared 

 by adding equal parts of water-soluble and alcohol-soluble safranin 

 to strong alcohol until a saturated solution has been reached. 

 The coloration with safranin is best carried on slowly and in dilute 

 solution, as in this way both clear detail and strong contrast are 

 best secured. Very often the best results follow from leaving the 

 sections overnight in the dilute safranin. In this instance, how- 

 ever, precaution should be taken to wash the sections very care- 

 fully and repeatedly after the use of iron alum and hematoxylin, 

 as otherwise disagreeable precipitates are likely to make their 

 appearance. 



Some plant tissues and remains show to best advantage 

 without staining. This is, for example, frequently true of darkly 

 colored heartwood and of fossil plants and coal. In the case of 

 the two latter it is often expedient to reduce the color by bleaching 

 agents. The most convenient method in this connection is sup- 

 plied by the use of chlorine water. Hydrogen peroxide, so often 

 recommended for bleaching vegetable tissues, is of no value in the 

 case of carbonized and fossil plant remains. When the dark colora- 

 tion is very intense, a more vigorous bleaching action results from 

 the use of nascent chlorine, which can be conveniently secured by 

 dissolving a few crystals of a chlorate in distilled water, with the 

 subsequent addition of a small quantity of nitric acid. This com- 

 bination gives sufficiently vigorous bleaching action without accom- 

 panying maceration. 



