CHAPTEE XXXII. 

 CELL-DIVISION AND NUCLEAR DIVISION. 



MATERIALS USED. 



Young flower-buds of Tradescantia Virginica, or allied species, June to 



September Fresh. 

 Flower-buds of various ages of some Liliaceous plant, such as Fritillaria 



Persica, or other species, Tulip, Lilium, etc. Fresh. Also the same in 



absolute alcohol. 

 Flower-buds, various ages, of a Ranunculaceous (such as Helleborus fcetidus] 



or Papaveraceous plant. Fresh. 

 Old internodes of Tradescantia Virginica. May to October. Fresh or 



in alcohol. 

 Stems, about f inch thick, of the Buckthorn, Rhamnus Frangula ; or twigs 



of the Mistletoe (Viscum album). 



KEAGENTS USED. 

 Very various. See text. 



Cell and Nuclear Division in Tradescantia. The best living 

 object upon which to follow directly the mitotic or indirect 

 division of the nucleus and the cell, is the staminal hairs of 

 the Spider- wort, Tradescantia Virginica, which we have already 

 used for the study of protoplasmic movements, or of some nearly 

 allied species. We must observe the hairs, however, in a stage 

 of development in which they are not yet fully formed, but 

 are in active cell-multiplication. For this purpose we take for 

 investigation flower-buds, which, without stalk, measure between 

 i and ^ inch in height. We open these buds, and first remove 

 the anthers from the filaments with fine fcurceps. Then with a 

 scalpel we cut across under the insertion of the ovary and the 

 filaments, and lift this part bodily out of the bud. We lay it in a 

 drop of 3 per cent, solution of sugar, and then set the filaments 

 free with needles under the simple microscope. The ovary and 

 all the other floral parts are removed from the preparation. We 

 can observe the preparation upon the slide direct, or on a cover- 



(434) 



