— 144 - 



As regards the embryo-formation in the genus Hieracium 

 investigations are chiefly presented by Mur beck (13) and Kirch- 

 ner (8), and according to these authors it is the egg cell, which 

 becomes embryo direct without fertilization. On the other hand 

 researches into the embryosac-formation in Hieracium have not 

 taken place, as far as the condition of the chromosomes is con- 

 cerned. As however it was shown, through Ostenfeld's continued 

 experiments, that the embryo-formation in Hieracium was much 

 more complicated, than one at first had reason to suppose, b ecause, 

 the same individuum was able to form seeds after fertilization (hybrid 

 formation) as well as after castration (apogamy), it was of course 

 necessary to make a cytological investigation and at the same time 

 especially of Ostenfeld's own material. It was therefore with 

 pleasure that I accepted Ostenfeld's invitation to cytologically 

 inspect his material as his experiments were, from time to time, 

 complete. 



I have in this way enjoyed a great advantage in the carrying- 

 out of my work, as my material, as regards its origin, was known 

 — a point of great importance here, when there is question of inve- 

 stigating the hybrid-formation. It was soon evident that the number 

 of chromosomes varied to a great extent in different Hieracium- 

 species and in the examination of hybrids it is necessary in con- 

 nection herewith to know T with absolute accuracy the parents of 

 the hybrid, so that, with a certain degree of safety, one can draw 

 conclusions regarding the origin. 



In the following treatise representatives of the groups P Hö- 

 sel la and Stenotheca will chiefly be described in detail. In 

 Murbeck's paper it is Archieracia which have been the subject of 

 investigation. During the progress of the work it was shown that 

 especially the cytology of the hybrids possessed so many peculiari- 

 ties, that a report therefore could better be postponed till the 

 coming summer could supply more complete material. 



The species more minutely described in the following are: 

 Hieracium auricula, venosum, excellens, flagellare and aurantiacum. 



First of all an embryologicai investigation was, of course, 

 necessary in order to explain the remarkable action of H. excellens 

 which could develop hybrid-seeds although apogamic (Ostenfeld 16, 

 p. 243 etc.). But besides this the reduction-process must be espe- 

 cially observed. This question however is connected with the 

 hybrid-formation which I intend in a following paper to treat 



