216 PEOTOPLASM. 



and the preparation verj' carefully washed. The application of 

 strong glj'cerin completes the treatment. The specimen must 

 uot be removed from the slide during the whole series of opera- 

 tions. If the manipulation has been careful throughout, the 

 minute threads can be seen passing from one mass of protoplasm 

 to the next. 



591. The directions given by Strasburger for demonstrating 

 the continuitj' of protoplasm are as follows : From the stem of a 

 dicotyledonous shrub or tree (the diameter of which should be 

 at least a centimeter) the periderm is removed by a knife, and 

 ver3- thin tangential longitudinal sections are then made through 

 the soft green bark. The parenchyma cells which are inter- 

 mingled willi the liber contain more or less chlorophyll, and may 

 have pits, the very smallest of which are not bordered (see 268). 

 If the first sections have shown in any case that these cells are 

 furnished with pits, others are then prepared and placed at once 

 in a drop of a solution of iodine (that of iodine in an aqueous 

 solution of potassic iodide is best). The excess of the solution 

 is at once removed and the preparation covered with a glass 

 cover. At the edge of the cover-glass there is placed a di-op 

 of concentrated sulphuric acid, and by the side of this a couple 

 of drops of dilute sulphuric acid ; when these ai-e mingled the 

 mixture is allowed to flow under the cover-glass, while a bit of 

 filtering-paper on the other edge of the glass draws it through. 

 The specimen becomes dark blue. If the color is deep, the cover- 

 glass is cautiously lifted and the preparation is tlien thoroughly 

 but carefully washed in water. After this wasiiing, a drop of 

 a solution of anilin blue is added, wherebj- the object becomes 

 stained ; then, after washing again, a little glycerin ' is added, 

 and the cover-glass is fastened down with some cement. For 

 the examination of the specimen the strongest objectives — pref- 

 erably the so-called "homogeneous immersion," employed with 

 cedar-oil — are indispensaljle. 



Under a sufficiently high power the middle lamella of the wall 

 is seen to be somewhat swollen, while the contents of the cells 

 are contracted and colored. The periphery of the individual 

 protoplasmic masses in the cells of the cortical parenchyma is 

 smooth on that face which was in contact with the cell-wall hav- 

 ing very small pits ; but it has minute protrusions on that face 

 which was next the bordered pits. Moreover, the protrusions 

 in contiguous cells are exactly opposite each other. Between 



• Strasbui'gev advises the addition of a little anilin blue to the glyoenn. 



