The Staining of living Nuclei. 577 



The first experiments were macle by immersing the base of the leaf- 

 stalk, which was generally split to facilitale Ihe action of the fluid, in a 

 rather strong, — -002 X to -001 % — , mauvein or dahlia Solution. After 

 being stained the epidermis was removed with a razor , or sections of the 

 inner parenchyma were used. In this way the nucleus was satisfactorily 

 colored, but the Streaming was usually very difficult to detecl. Later ex- 

 periments, staining directly on the sHde, were much better. 



Gare must be taken not to use too strong a Solution as the protoplasm 

 seems to be excessively sensitive. It was found that the color was taken up 

 almost instantaneously and the nuclei finely colored, butunless the Solution 

 was very dilute, the movement of the protoplasm was almost instantly stopped. 

 By using a dilute Solution, however, this may be avoided. 



"With dahlia a small drop of a -1^ Solution was diluted with three to 

 four parts of water and theu, as already described, run under the cover- 

 glass and allowed to remain about a minute, the time being regulated by 

 the color of the nucleus and the Streaming of the protoplasm which may be 

 watched under the microscope; the staining fluid was then replaced by 

 pure water. In this way excellent color and prelty active Streaming can 

 be had. 



With mauvein and methyl-violet used in the same way the result is 

 almost identical. 



The inner parenchyma of the leaf-stalk can also be used, but although 

 the nucleus colors readily the difficulty of making out the protoplasmic 

 movement is an objection. The protoplasm has almost disappeared from 

 these cells, and even in the unstained cells it is not always easy to detect 

 it, as the protoplasmic threads are excessively fine and the granules small 

 and few. 



Alisma plantago L. 



A few experiments were made with the inner parenchyma of the base 

 of the leaf-stalks oi Alisma with similar but less satisfactory results to those 

 reached with Sagittaria. The nuclei are not so large and seldom lie enti- 

 rely free being usually partially hidden by Chlorophyll granules or starch- 

 grains. The nuclei moreover do not stain nearly so well and tliere is a more 

 or less pronounced precipitate formed in the cell sap by the coloring agent. 

 On the other hand the Streaming is much easier to demonstrate as the pro- 

 toplasmic threads are larger and more numerous. 



Vallisneria spiralis L. 

 Occasionally a good nuclear stain was observed with Vallisneria, but 

 it is very uncertain. In making preparations either longitudinal sections of 

 the leaf were used, or eise the thin, nearly colorless margins of the basal 

 part of the leaf. In all of the cells, as is well known, the rotation of the 

 protoplasm is extraordinarily well marked. 



