572 Douglas H. Campbell. 



remain attached lo Ihe receptacle. The bud tlius prepared is immersed in 

 the staining fluid. Owing lo the difficulty of freeing the preparation from 

 air, it is difficult to make exact calculations as to tlie time neeessary for 

 coloring. The Solutions used varied from -002 % to .0002 % and were 

 for the most part dahlia or mauvein. From one to two hours was usually 

 sufficient with the strenger Solutions, -002 % to -001 %, to give with 

 many of the cells a decided coloring of the nucleus; the hairs may be left 

 in weaker Solutions from 8 to 1 hours, or even longer vvithout injury. 



As before stated, owing probably in great part to the accumulation of 

 air, and possibly also to the unequal cuticularisation of the walls, many of 

 the cells remain entirely uncolored. If the Solution is too concentrated 

 there is apt to be coloring of the walls which of course interferes with a 

 determination of the amount of nuclear coloring : the protoplasm is as a 

 rule, but slightly stained. 



When the staining has been successful, the appearance of the cell is 

 perfectly normal and the protoplasmic Streaming can easily be seen ; 

 the nucleus has assumed a more or less pronounced blue or violet color, 

 varying a good deal with the amount of the coloring matter absorbed, but 

 in the most favorable cases it is surprisingly deep. The nucleus remains 

 absolutely unchanged in form and structure, in very streng contrast to the 

 hard sharp outline and contracted appearance of the nuclei that have 

 been killed in the process of staining. There are usually a number of such 

 nuclei in every preparation which serve as objects of comparison. The 

 color, too, of the living nuclei is much softer than in the dead ones, the 

 latter being of a most intense violet purple. whereas the living nuclei are 

 generally rather of a blue-purple. 



With both dahlia and mauvein the dividing nucleus was colored a 

 number of times, and with the first it was possible to follow through the 

 division as the nucleus in a few cases observed continued the division 

 after being stained. In one case in particular the division was completed 

 in a perfectly normal manner. 



In this instance the hairs had been left for 1^4 hours in a 002 % So- 

 lution of dahlia and one of the nuclei was observed to be pretty well ad- 

 vanced in the process of division. The two parts were only slightly sepa- 

 rated and the Segments still distinct. Protoplasmic Streaming could be de_ 

 tected, and as the nucleus was watched it was seen to be changing. 



The first Observation was made at 10.30 a. m. At this time the clear 

 Space between the two portions of the nucleus was scarcely to be seen 

 and the most careful scrutiny failed to detect any sign of the formation of 

 a division-wall, but the movement of the protoplasm appeared to be most 

 active toward the center of the cell. Shortly after the beginning of the ex- 

 periment an indistinct line, apparently formed by the aggregation of mi- 

 crosomes, was to be seen in the middle of the space between the daughter- 



