1900] MICROSCOPICAL JOURNAL. 65 



riu, carbolized water, and solutions of the salts mention- 

 ed exhibit the cell walls more nearly in their natural con- 

 ditions as to thickness than do those mounted in the re- 

 sins ; the contours of the cells and of the cell contents, 

 starch, crystals, etc., are also much more clearly defined ; 

 but the field of view is darker and the tissue systems are 

 not 80 well differentiated as in Canada balsam. Grener- 

 ally only stained material is mounted in Canada balsam, 

 and the colored cell walls stand out with great clearness, 

 while the unstained cell contents are to a great extent 

 suppressed from the field of vision. The various kinds 

 of tissue may be readily distinguished, but the charac- 

 ters of the cells are not so evident because of the dehy- 

 drating process to whicli the material has been submitted, 

 the cellulose walls being thin and often wavy. Starch is 

 occasionally mounted in balsam for the purpose of exam- 

 ining it with polarized light, but the medium is a most un- 

 suitable one for exhibiting the general characteristics of 

 starch. 



Stains. — Sections are generally stained with two col- 

 ors, green and red being the favorite ones. If the cell 

 contents have been removed it will not be difficult in such 

 slides to distinguish between the lignified tissues, which 

 are stained green, and the cellulose tissues, stained red. 

 Carmine and hsematoxylin are the stains usually used for 

 cellulose. The former of these, when used as a general 

 stain, does not attack the lignified tissues, but the latter 

 does so to a varying extent, so that in the absence of a 

 counter-stain, the distinction between cellulose and lig- 

 nified tissue is not at all clearly marked! Indeed, the in- 

 tensity of color diminishes in proportion to the extent to 

 which the lignification has taken place. Therefore the 

 student cannot rely upon hjBmatoxylin as a means of sep- 

 arating lignified from non-lignified tissues. In connec- 

 tion with hsematoxylin and carmine it should be remem- 

 bered that the section may have been cut from fresh ma- 



