— 157 — 



that hero the reduction process has been carried out irre- 

 gularity. 



In a later stage of development of the ES one could observe 

 competition between the two embryo sacs. In certain cases the 

 tetrad was destroyed in a stage when the embryo sac cell had not 

 yet begun to divide. And again in such cases it is almost impossible 

 to determine if the growing ES is the typical one or of aposporic 

 origin (Fig. 31). However it often happens, that both ES simultane- 

 ously could be developed and in such cases all intermediate stages 

 between complete destruction of the typical ES and the complete 

 development of both ES can be seen. 



The fig. 28 depicts the typical Es in the anaphasis of the se- 

 cond division, the aposporical ES has significantly developed in 

 every direction. It gives the impression as if the typical ES ob- 

 structed the aposporic ES from pressing down into the nucellus 

 cavity. The figure shows very clearly the different number of 

 chromosomes in both the ES: the one below with about 17, the 

 upper one with about 34 chromosomes. A comparison of the fol- 

 lowing sections showed, that the aposporic ES had 8 nuclei which 

 however divided simultaneously into 16 nuclei. I shall later on in 

 the present treatise return to this exceptional case. 



Fig. 30 shows the typical ES in the 2-nucleus stage (the 

 second nucleus lies in the following section), whilst the aposporic 

 ES is also in the 2-nucleus stage, but it has already encroached 

 the typical ES. Judging from the size of the nuclei the lower ES 

 has the reduced number of chromosomes and the upper one the 

 unreduced number. 



Fig. 29 represents a somewhat similar stage. The 2-nucleated 

 aposporic ES has developed a little later, whilst the typical ES is 

 already fully developed. An shows an antipodal cell and under 

 this lies a polar nucleus. 



Fig. 32 depicts the other extreme stage with two fully deve- 

 loped ES. the upper of which is probably of aposporical origin. 



H. flagellare. 



The ES-formation in H. flagellare proceeds in about the same 

 manner as in H. excellent, the apospory is, however, much more 

 common. In nearly every ovule one can find such aposporical 

 ES. Very often the origin of this ES is a cell going deeper down 



Botanisk Tidsskrift. 28. Bind. 11 



