248 



BO TA NIC A L MICRO TE CHNIQ UE, 



It may be observed that Gardiner finds it useful to brush 

 over the sections with a earners-hair brush after swelling 

 and staining. 



454. A method differing essentially from previous ones has 

 lately been used by Kohl (I, 12) for demonstrating the proto- 

 plasmic connections. It agrees in essence with Loeffler's 

 method for staining cilia ( 476). After preliminary mor- 

 danting with tannin, Kohl stained with methylene blue or 

 Bismarck brown ; and if the staining of cell-walls or gelatin- 

 ous sheaths, due to the presence of pectic substances, inter- 

 fered with observation, these substances were removed by 

 an acid. This author has not given more exact details of 

 his method. 



23. Contents of Sieve-tubes. 



455- Since the contents of the sieve-tubes, which com- 

 municate by relatively large openings, are partly pressed 

 out on cutting the tissues, and undergo the most various 

 changes, A. Fischer (III) has devised a method of fixing the 



FIG. 63. Parts of sieve-tubes of Cucurbita Pepo. a, from a plant cut and then scalded; 

 j, " Schlauchkopf "; b, scalded in an uninjured condition (x 675). After Fischer. 



contents of the sieve-tubes in the uninjured tissues. For 

 this purpose he plunges carefully unpotted plants or pieces 

 of an uninjured plant, such as branch-tips, into boiling water 

 and leaves them in it until the contents of the sieve-tubes 

 are coagulated, for which two to five minutes' exposure is 

 usually quite sufficient. He was able to show that the 

 accumulations of strongly refractive and readily staining 

 substance observed at one side of the sieve-plate in Cucur- 



