ee ee ee ee dete a ie ee ra ee ey oe he iW re ene, ae ho ee eee 
1903] EMBRYO SAC OF CASUARINA 113 
Fic. 6. Nucellus: s, massive sporogenous tissue within, with well defined 
lateral limits. « goo. 
IG. 7, Spore mother-cell about to divide, showing chromatin threads ; 
the cells are longer, the section is diagonal. X I950 
I Row of four megaspores; #, micropylar end. X Ig5o0. 
Fic. 9. Row of four megaspores, the middle ones enlarging; ™, micro- 
pylar end. X 1950. 
Fig. 10. Row of four megaspores in various stages of embryo sac for- 
Bil sl mM, sca end. X I950 
Fic. 11. Two-celled embryo sac; antipodal prolongation (a) already 
begun. X aa 
Fic. 12. Two-celled embryo sac; m, micropylar end; no well defined 
se prolongation. X Ig50. 
13. Four-celled embryo sac; a, possibly beginning of antipodal 
i ees X 1950. 
F1G. 14. Row of four megaspores derived from one spore mother-cell 
and older than those in fg. 70; m, micropylar end; A, arrested megaspore ; 
B,megaspore probably arrested after some internal cell division, but now 
disintegrating ; C, 8-celled sac; a, 4, ¢, d, will probably form egg apparatus 
and micropylar polar; ¢, probably antipodal polar; /, antipodals with sug- 
gestion of wall formation; D, 7 or 8-celled sac with antipodal prolongation : 
h, t, 7, probably antipodal and polar or endosperm cells. X 1950. 
Fig. 15. Eight-celled embryo sac; a, antipodal; Z, point where antip- 
odal projection may be expected to arise; fo, polar nuclei. X 
Fig. 16. Typical embryo sac without the long antipodal prolongation ; ¢, 
endosperm nucleus; a, antipodals. x 1950. 
1G. 17. Embryo sac with more elongated cells in egg apparatus; only 
two antipodals found; a, polar nuclei or one endosperm and the other antip- 
odal. X IQ50. 
Fig. 18. Pollen tube approaching the nucellus; 4, branch of tube; dot- 
ted line bounds sporogenous tissue. X 140. 
Fic. 19. Part of fig. 78 enlarged; ¢, tube nucleus, s, sperms. X 1366. 
Fic. 20. Pollen tube just having reached the embryo sac; ##, pollen 
tube; ¢, tube nucleus; s, sperms; a, antipodals; #, polars, one nucleus in egg 
apparatus and one antipodal missing. X 1950. 
Fig. 21. A case of double fertilization; s, sperms; antipodals not found 
in this preparation. X 1950. 
