148 BOTANICAL MICROTECHNIQUE. 



stained deep red and pure cellulose membranes violet or 

 blue. 



260. Acid fuchsin* gave me similar preparations, which 

 were washed either with running water or with Altmann's 

 picric acid solution (cf. 345-6). Aml'me-water-sa/ranm 

 also gave me preparations in which only the lignified and 

 suberized walls were stained after being washed out with 

 acid alcohol (cf. 268), after acting for at least an hour. 

 Gentian violet acted in the same way when used according 

 to Gram's method (321). All these preparations maybe 

 well preserved in Canada balsam, and the dyes may be used 

 for double staining in the way above described. 



261. The staining methods named may be very well used 

 for the demonstration of the course of the vascular bundles 

 in whole parts of plants, such as leaves or thin stems. I 

 obtained very instructive preparations with a concentrated 

 aqueous solution of fuchsin under which I cut off the part 

 to be stained, so that the vascular bundles were mostly 

 deeply stained in a relatively short time. When this was 

 accomplished, I placed pieces of the objects in alcohol until 

 the chlorophyll was completely removed, cleared them in 

 clove-oil, and transferred to Canada balsam. Especially 

 favorable objects for study are found in the leaves of Secale 

 cereale and of Impatiens parviflora. In the latter only the 

 tracheal elements were colored red, and could be very 

 clearly seen even in the thicker parts. 



3. The Cuticle and Suberized Membranes. 



262. Until recently it has been generally assumed that 

 suberization is due to the incrustation of the cellulose wall 

 with a fat-like substance commonly called suberin. This 

 assumption has been based especially on the observation 

 of Fr. von Hohnel that suberized membranes are colored 

 red-violet with chloroiodide of zinc after treatment with 

 an aqueous solution of caustic potash. But the recent 



* This dye is also called " Fuchsin S," and by Dr. Griibler, " Fuchsin S 

 after Weigert." 



