1 



117 



The whole process under proper conditions, is completed in 

 about two hours, but care must be taken that the temperature of 

 the water in which the specimen is mounted is about the same as 

 that from which it is taken. A marked rise of temperature is 



apt to kill the cells. 



For studying the complicated changes that the nucleus under- 

 goes during cell-division, as well as the method of the formation 

 of the division- wall as it usually occurs, we must examine some 



of the higher plants. 



For following the process in the living cell, probably no plant 



is better than Tradcscantia Virginica. 



Strasburgcr showed* that the stamen hairs of this plant were 

 especially useful for this purpose, and has described the process 

 so fully in several places that it will not be repeated here. For 

 examination it is only necessary to carefully remove the stamens 

 from young buds and mount them with the attached hairs in 

 water or a weak (three per cent.) solution of sugar in water. It 

 is possible to stain thcset without killing them, by using a weak 

 aqueous solution of methyl-violet, dahha or mauvein but very 

 Httle more can be seen than in the unstained cells and the pro- 

 cess of division is retarded. 



For easy demonstration of the process of karyokinesis, the 

 final divisions of the pollen mother-cells, especially of monocoty- 

 ledons, are the best subjects. 



Among dicotyledons which, as a rule, are unfavorable for 

 showing the finer details of the nuclear divisions, Podophyllum 

 peltaUun is a conspicuous exception, and the process will be de- 

 scribed somewhat in detail for this plant, with some reference 

 also to a common and easily studied monocotyledon, Allium. 

 Canadeiisc. In Podophyllum buds should be taken just as the 

 plants appear above ground in the spring. The same young 

 umbel of Allium often furnishes different stages, and with a lit- 

 tle care all stages may be found, and very satisfactorily shown 

 by the following simple method : The young anthers are removed 

 and carefully crushed in a drop of equal parts ordinary acetic acid 



i 



^Strasburger— Ilillhouse, Practical llotany— (p. 35^»). 



fCampbell— *• Staining of living nuclei/' Arbeiten des Bot. Instituts zu Tubin- 

 gen, l8S8. 



