Experimental and Cytological Studies 

 in the Hieracia 



by C. H. Ostenfeld and O. Rosenberg. 



II. Cytological Studies on the Apogamy 



in Hieraeium 



by 



O. Rosenberg. 



(With two plates.) 



When Raunkiaer (20) and Ostenfeld (17) succeeded by 

 means of their experiments in pointing out that embryo formation 

 without fertilization took place within the genera Taraxacum and 

 Hieraeium, it was naturally of great importance to show, with the 

 help of an embryological and also cytological investigation, in what 

 form the „apogamy" appeared here. 



Soon after Raunkigers announcement Juel (6) published a 

 preliminary statement concerning his observations regarding embryo- 

 sac formation in Taraxacum, and later on (7) a more complete 

 paper on the tetrad division in some representatives of Compositae, 

 in which among other species Taraxacum is minutely described. 

 It was shown that only one division, and with an unreduced 

 number of chromosomes, was to be found in the embryosac 

 mothercell, whilst in the pollen-mothercell a complete reduction 

 division took place. 



Murbeck (13) afterwards pointed out that in the genus 

 'Taraxacum the eggcell without fertilization developed to embryo, 

 and if we connect this with Juel's discovery, then the embryo- 

 formation is here about the same as in Antennaria alpina (Juel, 5) 

 with exception of the fact that in this case the EMC 1 ) develops 

 direct into an embryosac. 



] ) In the present paper I will use the following abbreviations: PMC = Pollen 

 inothercell, EMC = Embryosac-mothercell and ES == Embryosac. 



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