— 163 — 



Very extraordinary complications appear, when both a typical 

 and aposporic ES are developed in the same ovule. A number of 

 such stages are shown in fig. XI. tn fig. A there are two ES, 

 of which the left one has already developed endosperm and embryo, 

 the one on the right is probaby the typical ES which has not 

 developed further, as no fertilization has taken place. The apo- 

 sporic ES has already removed the possibility of fertilization, in 

 filling up the entrance to the typical egg cell. 

 In fig. B an apparently later stage is repre- 

 sented. The typical ES is quite enclosed in 

 the endosperm of the aposporic ES. One can 

 still observe the egg cell and two polar nuclei. 



The case in fig. XI C is really most curi- 

 ous, where two ES appear, both with endo- 

 sperm and embryo. Perhaps one is a typical 

 one which has been fertilized and the other 

 an aposporic one which has grown round 

 the other. 



Very often one meets ovules with two ES 

 of a significantly different stage of development. 

 In the farther one the egg cell is still undi- 

 vided, whilst the one behind seems to consist 

 only of endosperm cells. I have never been 

 able to find embryo in such cases. It seems 

 to me that this is the final stage of the case 

 depicted in fig. 28, in which the lower ES 

 was typical and the one behind aposporic 

 with eight dividing nuclei. 



Fig. XIII represents a peculiar case where 

 the embryo of the aposporic embryo sac is 

 istuated in the antipodal region and perhaps 

 originates from an antipodal cell. 



Fig. XIII II. flagellare, 

 aposporic embryo sac 

 with an embryo, E, at 

 the antipodal end, A ; M, 

 the mikropyle with the 

 rests of the typical ES ; 

 S, synergids; C, endo- 

 sperm nucleus. 



Results. 



The preceding statements show that a remarkable variation 

 as regards the embryo formation is to be found in the group Pilo- 

 sella of the genus Hieracium. 



In H. auricula (as in H. venosum of the Stenotheca-group) 

 the embryo sac formation is quite normal and fertilization is 



