476 
Sargant. — The Formation of the 
Fig. 9. Nucleus from young nucellus. 
Fig. 9. Nucleus in early spindle from hypodermal cell occupying a median 
position in a young nucellus and therefore a possible ancestor for the embryo-sac. 
x 1000. 
Figs. 10-12 a . Nuclei from embryo-sac. 
Fig. 10. Median optical section of resting primary nucleus. X585. 
Fig. 10 a. Tangential view of same. The chromatic thread shows a single row 
of dots, x 1050. 
Fig. 11. Later resting stage, n nucleolus, x 585. 
Fig. 11 a. Part of chromatic thread (x, fig. 11), more highly magnified. It still 
shows a single row of dots. 
Fig. 12. Transition to synapsis. The thread has thickened and the dots are 
larger, x 585. 
Fig. 12 a. Part of chromatic thread more highly magnified. The thickened 
thread shows a double rows of dots, n n lumps of nucleolar matter. 
Plate XXIII. Lilium Martagon. 
Figs. 1 3-43. Nuclei from embryo-sac. 
Fig. 13. Primary nucleus in synapsis. Chromatic thread contracted. Nucle- 
olus sickle-shaped. Membrane obscure. X585. 
Fig. 13 a. Part of thread from younger nucleus during synapsis more highly 
magnified. It is hardly broader than that shown in Fig. 12 a. 
Fig. 13 £. Part of thread from tangential section of nucleus shown in Fig. 13, 
magnified to same extent as Fig. 13 a. It is broader than that of Fig. 13 a, but the 
dots are no larger. 
Fig. 14. Primary nucleus in spirem. x 585. 
Fig. 15. Similar nucleus rather later. The chromatic ribbon begins to split 
longitudinally while still continuous. X585, 
Fig. 16. Similar nucleus just after segmentation, x 585. 
Fig. 17. Primary nucleus soon after segmentation. The long double segments 
show a tendency to cluster round the washy nucleolus, and the membrane becomes 
obscure, x 585. 
Fig. 18. Primary nucleus a little later. The long segments have contracted and 
cluster round half-dissolved nucleolus. Each semi-segment shows signs of longi- 
tudinal fission. The membrane is obscure. x 585. 
Fig. 19. Primary nucleus at stage a good deal later than that shown in Fig. 18. 
Median section of series. Each immature chromosome consists of two ribbon-like 
segments which are bordered on either margin by a row of chromatic granules. 
Membrane broken, perhaps accidentally. The chromosomes are clustered round 
the nucleolus, which now has a definite outline, x 585. 
Fig. 19 a. Single immature chromosome at stage corresponding to that of Fig. 19, 
but from a tangential section of another nucleus, x 1050. 
Fig. 20. Primary nucleus with mature chromosomes just before disappearance of 
nuclear membrane. Traces of the cluster round the nucleolus persist, x 585. 
Fig. 21. First karyokinesis. Five chromosomes from early spindle. Drops of 
nucleolar matter scattered over spindle and cytoplasm, x 585. 
Fig. 22 (■ a-c ). Three successive sections of a single nuclear plate (first karyokinesis). 
There are unmistakably twelve chromosomes, x 585. 
