34 THE STRUCTURE AND DIVISTON OF THE VEGETABLE CELL. 



tain phases till the equatorial plate is reached ; then passing 

 again through the same phases, but in reversed order, they 

 (the daughter nuclei) again reach the resting condition. 



The figures assumed by the nuclei during division vary some- 

 what amongst the different classes of plants, but still in all essen- 

 tial particulars they agree. In Figs. 11 to 14 are shown the ap- 

 pearances presented by the two elements in the nucleus of the 

 spore mother-cell of Equisetum limosum. You will notice how 

 much more regular in outline and arrangement they are. It is 

 needless to describe the process here in full, as it agrees with 

 that given in the Tulip. I would, however, point out that in Fig. 

 13 you have two nuclei in process of division, one further advanced 

 than the other, but in one the equatorial plate is shown in plan, and 

 appears almost solid. The spore mother-cell is without a wall till 

 the stage in Fig. 14 is reached, when cellulose is deposited around 

 the cells, which have now become the spores. 



That these structures and processes are of great interest and 

 importance we must all admit, but at present it is impossible to 

 say which of the two nuclear elements is to be looked upon as 

 the efficient cause of the phenomena we have been reviewing. Is 

 it the achromatin, as suggested by Flemming, which acts upon 

 and causes the chromatin to pass through the varied figures in 

 which we ha^e seen it? or is it in the chromatin that the power 

 resides, and by which it operates, imparting what may be called 

 polarity to the colourless element, and so arranging it as has been 

 described, and bringing about the final division by its agency ? 

 For an answer to these questions we must wait for more light. 



DESCRIPTION OF PLATE I. 



Figs. 1-10. — From integument of ovnleof Tulipa Gesneriana. Figs. 11-14. 



— Spore mother-cells of Equisetum limosum, all X 570. 

 Fig. 1. — Nucleus in resting condition. 

 Figs. 2-10. — Successive stages in division of Nuclei. 

 Fig. 5. — Nuclear spindle with equatorial plate. 

 Fig. 8. — Dyaster stage. 

 Figs. 9, 10. — Appearance of Nuclear plate, showing position of future 



cell plate. 

 Fig. 11. — Nuclear spindle with equatorial plate. 

 Fig. 12. — Division of equatorial plate. 

 Fig. 13. — Equatorial plate seen in plan in one daughter cell, and further 



separation in the other. 

 Fig. 14. — Final stage, just prior to separation of spores. 



