— 162 — 



However most of the ES are of aposporic origin, especially in 

 H. flagellare, where consequently the egg cell has the unreduced 

 number of chromosomes. It is not necessary for such an egg to 

 he fertilized, but it continues directly the embryo formation as in 

 other apogamic species. In ordinary cases therefore in Hieracium 

 a normal seed is developed where, however, the embryo and endo- 

 sperm are of vegetative origin. 



A B 



Fig. XII. H. excellent; A, ovule with one aposporic and under this one typical 

 embryo sac; B, the typical embryo sac enclosed in the endosperm of .the 



aposporic one. 



Fig. X shows a remarkable anomaly which is quite often met 

 with. There are two embryos in the same ES. The adventive 

 embryo is, however, in this case not of the same value as for 

 instance in the ordinary „Nucellarsprossungen" in several plants, 

 but its origin is an endosperm cell which is shown in fig. X, B. 

 It may possibly depend upon the fact that the polar nuclei have 

 not become united, and the one of them is the cause of the 

 embryo formation. I have not yet determined the number of 

 chromosomes in the cells of such embryos which must be 68, if 

 the polar nuclei have been united. 



