14 Biological Stain.s 



stains and stains for woody tissue. This grouping is no more 

 absolute, however, than the separation between general tissue 

 stains and connective tissue stains in the zoological field. Prob- 

 ably the most frequently used dye in botanical microtechnic is 

 hematoxylin, which is employed in a number of procedures either 

 for general tissue or woody tissue. Another very valuable dye is 

 safranin which is one of the best nuclear stains employed in 

 botanical work; with a green or blue counterstain, very effective 

 pictures are obtained. 



Various combinations of stains have been employed for certain 

 more highly specialized purposes, such as staining fungi in tissues, 

 or for demonstrating pollen tubes in the style. For such purposes 

 as this, numerous dyes have been called for, such as thionin, 

 orange G, martins yellow, malachite green, acid fuchsin, methyl 

 gjeen, carmine, basic fuchsin, and lacmoid. It is nevertheless 

 true, as stated above, that there is by no means such a variety of 

 staining procedures in plant histology as in the zoological field. 



Plant Cytology. Although the statement just made is true in 

 the general histological field, it cannot be made in regard to cytol- 

 ogy. The earliest cytological work was done with plant material, 

 probably because of the greater ease with which rapidly dividing 

 cells (meristematic tissue) can be obtained from plants than from 

 animals. The result is a very considerable variety of procedures 

 in plant cytology. Best known among them, undoubtedly, are: 

 the variations of the hematoxylin methods; the Flemming triple 

 stain, which calls for crystal violet, safranin, and orange G; and the 

 aceto-carmine method employed for fresh smears of anthers. There 

 are numerous special combinations of crystal violet and of safra- 

 nin, each with particular counterstains designed to bring out certain 

 desired effects. 



It is interesting to note that, although there are many dyes used 

 in both plant and animal microtechnic, there are others that are 

 important in one of these fields but not in the other. Thus car- 

 mine and safranin are pre-eminently botanical stains, methylene 

 blue a very important zoological stain that is hardly ever em- 

 ployed by the botanist. 



Microbiology. Another very important field in which biological 

 stains are employed is the study of bacteria and related micro- 

 organisms. The dyes thus used are somewhat limited in number, 

 methylene blue, crystal violet and basic fuchsin satisfying most of 

 the bacteriologists' needs. It is very interesting, however, to 

 note that these three dyes, which are pre-eminently bacteriological 

 stains, are by far the largest sellers of any of the biologicals. This 

 indicates that although the bacteriologist does not employ as 

 many staining procedures as the worker in other fields, he is by far 

 the most important customer, in point of quantity ordered, of any 

 to whom the manufacturer supplies these products. 



