246 BOTANICAL MICROTECHNIQUE. 



material, and at once dropping on a cover-glass to prevent 

 too great warping of the sections. After a short time the 

 -whole slide is plunged into a large vessel of water in which 

 it remains until the sections have become clear violet. Al- 

 though the cover-glass usually separates from the slide, some 

 sections generally remain attached to it, and these can, 

 naturally, best be used for study. 



451. A very deep staining of the protoplasmic connections 

 contained in the sieve-pores may be obtained in microtome 

 sections of stems of Cucurbitacece by the use of Altmann's 

 acid fuchsin method (cf. 345). This brings out the proto- 

 plasmic threads without the previous use of any swelling 

 media. 



In many cases the double staining, described in 290, 

 with aniline blue and eosin gives very fine preparations of 

 the sieve-plates with the protoplasmic connections passing 

 through them. 



452. Delicate protoplasmic connections, on the other hand, 

 liave as yet been made visible only by the successive action 

 of swelling and staining media. 



For swelling, chlorolodide of zinc and sulphuric acid have 

 Ibeen chiefly used. 



Chlorolodide of zinc was recommended especially by 

 ^Gardiner (II). He treated sections of fresh material first 

 -with a solution of iodine and potassium iodide, then added 

 -chloroi'odide of zinc and let it act a longer or shorter time, 

 according to the capacity of the membranes for swelling, 

 commonly about 1 2 hours. Before staining, the chloroiodide 

 ^vas washed out with water or, where the membranes were 

 much swollen, with alcohol. 



453. When sulphuric acid is used, the sections are also 

 usually first fixed with iodine and potassium iodide solution. 

 Kienitz-Gerloff (I, 8) used for this purpose a solution con- 

 taining .05 gram of iodine and .20 gram of potassium iodide 

 in 15 grams of water. He recommends, especially for juicy 

 tissues, the method used by A. Fischer (III) with the best 

 results in the study of the contents of the sieve-tubes (cf. 

 455). This author scalded large plants or large parts of 



