I $2 BOTANICAL MICROTECHNIQUE. 



Both of these stains are of interest as indicating anew 

 that fat-like substances are deposited in the cuticle and cork. 



26ya. I have recently found that, besides alcannin, which 

 gives a very deep staining of the cuticle after long action, 

 asmic acid and cyanin may be also used for the recognition 

 of suberized membranes. For this purpose, I dissolve cya- 

 nin in 50$ alcohol and add an equal volume of glycerine. 

 Preliminary treatment of sections with eau de Javelle is gen- 

 erally to be recommended, as it destroys the tannins which 

 hinder the staining. It also causes the lignified walls to lose 

 their power of staining, while suberized ones are as deeply 

 stained as in the fresh condition, even after being exposed 

 for a day to its action (cf. Zimmermann VII). 



268. In their behavior with staining media, the cuticular- 

 ized and suberized membranes show in many respects an 

 agreement with lignified ones. This is especially true of the 

 so-called suberin lamella of cork-cells ; but the true cuticle 

 is often less easily stainable. But it is usually easy to stain 

 the cuticular layers differentially, especially in thick-walled 

 epidermal cells ; and double stainings, in which these layers 

 are differently colored from the cellulose layers lying be- 

 neath, may be obtained. But it must be remarked that these 

 stains do not always act with the same precision, in all cases, 

 as with lignified walls; and different plants do not appear to 

 behave in the same way in this respect. I recommend as 

 suitable objects for study, the leaves of Clivia nobilis or Agave 

 aniericana. On these the following stainings and double 

 stainings may be readily carried out. The statements as to 

 time refer to microtome sections. 



a. Safranin. 



269. The best staining medium for suberized walls is ani- 

 line-water-safranin, prepared by mixing equal volumes of ani- 

 line-water and a concentrated alcoholic solution of safranin. 

 I allow this to act for half an hour or longer on the sections, 

 then cover them with acid alcohol,* which is quickly replaced 



* That is, alcohol to which is added about .5$ of the ordinary chemically 

 pure HC1. 



