(5) 



EXPLANATION OF FIGUEES. 



All sections were cut with a Cambridge rocking microtome, the thickness 

 varying from 5 fi-lO fi. The figures were drawn with the aid of a Zeiss microscope 

 and a Zeiss camera lucida. Figs. III. 6, X., and XI. with a Zeiss yj-in. oil 

 immersion objective. The sections are cut transverse to the axis of the ovary, 

 thus giving longitudinal sections of the ovule. 



In all Figs. O.W. = Ovary wall. 



O.I. = Outer integument. 



I.I. = Inner integument. 

 M.M.O. = Megaspore mother-cell. 



N. = Nucellus. 



E.S. = Embryo-sac. 



E.C.N. = Egg-cell nucleus. 



S.N. = Synergid nuclei. 



P.N. = Polar nucleus or nuclei. 



D.N. = Definitive nucleus, 



FIG. 



I. Young ovule about megaspore mother-cell stage, x 184. 



Il.a & 6. Young ovules showing megaspore mother-cell each, x 184. 



III. a. Young ovule showing stage of development at first division of megaspore 



mother-cell, x 104. 

 III. 6. Central part of same section more highly magnified, x 760. 

 IV. Young ovule showing second division of megaspore mother-cell. 



X (circa) 200. 

 V.a. Young ovule showing development of functional megaspore. x 68. 



V.6. Central part of same section more highly magnified, x 320. 



VI. a. Young ovule showing four-nuclear embryo-sac drawn from two sections. 



x 104. 

 VI. 6. Central part of same sections more highly magnified, x 184. 

 VII. a. Eight-nuclear embryo-sac. Drawn from three sections, x 184. 

 VII. 6. Another embryo-sac showing same stage. Drawn from two sections. 



X 288. 



VIII. Embryo-sac in slightly later stage. Drawn from two sections, x 160. 



IX. Embryo-sac after migration of both polar nuclei. Drawn from three 



sections, x 184. 



X. Micropylar end of mature embryo-sac showing two synergidse egg- 



nucleus and definitive nucleus. The latter still shows two distinct 

 nucleoli, x 656. 

 Xl.a-f. Stages of karyokinetic division, a-c. In plane of division, d-f. In 

 equatorial plane. 



a x 880 6 X 880 ex 880 

 cZ X 760 e X 880 f x 760 



