PLATE XII. 



{The Figures are from, Strasburge/s work ' Ueber Zellbildung uni Zelltheilung .') 



Figs. 1 — 6. — Free-cell formation in Phaseolus muUiflorus. (Alcoiiolic 

 preparations.) 



I. Earliest beginnings of an endosperm-cell in the looser portion of 



the peripheral protoplasmic layer of the embryo-sac; the 



nucleus is still punctiform. 

 2 — 6. The same at later stages. 

 Figs. 7 — 10. — Cell-division in Picea vulgaris. 

 Figs. 11, 12. — Cell-division in Pinus sylvestris. 



7. The four' nuclei which appear at once in the embryonal vesicle 



after the original nucleus has vanished. 



8. Optical section of the same part of the embryonal vesicle. 



9. Preparations for division ; in the left-hand nucleus the nuclear 



disc has already split into two. 

 10. A later stage than in 9 ; the equatorial cell-plates. 



II. Immediately after the formation of the new nuclei ; cell-plates 



well marked. 

 12. The cellulose membrane already separated out between the 

 two laminae of the cell-plate. 

 Figs. 13 — 16. — Cell-division in Phallusia mamillata. 

 Fig. 17. — Cell-division in CucuUanus elegans (after Biitschli). 

 Fig. 18. — Cell -division in Blatta germanica (after Biitschli). 



13, 14. Commencement and migration of the nucleus in fertilised 

 ova (alcoholic preparations). 



15. Elongation of nucleus and formation of nuclear disc (alcoholic 



preparation). 



16. Division of nucleus (fresh preparation). 



17. A dividing ovum. In the upper cell the nucleus is spindle- 



shaped and striated, the nucleus disc having just divided. 



18. Nuclear plate or disc has just divided. 



Fig. 19. — Development of new nuclei and formation of the division be- 

 tween the cells {Ginkgo Vilobd). 



Fig. 20. — Upper four cells of a hair from a stamen of Tradescantia 

 virginica ; the highest still dividing ; the lower two have just arisen by 

 division within their mother-cell. 



