MISCELLANEA, 



Apogamy and Hybridisation. 



3Ir. C. H. Ostexfeld, of Kohfuhav!., who in 1906 brought 

 out a paper on Apogamy and Hybridisation of the Hieracia, 

 popularly known as Hawk-weeds, repeating some of Mendel's 

 experiments, has just pubUshed an accoimt of the results of 

 some further experiments on apogamy and hybridisation of the 

 Hieracia from 1906 to 1909.* The plants experimented on 

 were obtained from a wide area, north, south, east, and west of 

 Europe, and included many from North America, besides the 

 offspring of previous experiments. 



The method of castration was a complete shave with the 

 razor, cutting off the top of the unopened head within two or 

 three days of expansion ; this operation removed all the stigmas 

 and anthers. Every precaution was taken to ensure isolation 

 of the seed, the soil in which it was sowed being first baked — 

 very necessary when experimenting with such a common and 

 widely distributed genus as the Hieracia. 



The experimental results obtained by Mr. Ostenfeld as the 

 outcome of castration of the flower heads, suggested the necessity 

 of a cytological investigation of the embryo sac and surrounding 

 nucellus of the ovules. Prof. 0. Rosenberg undertook this. He 

 made examinations of the developing apogamous ovules and found 

 the chromosomes of the egg-cells unreduced, i.e., their number 

 equalled those of the body cells. 



Mr. Ostenfeld carefully summarises all the current theories 

 on the connection between mutations, their constancy, and 

 apogamy ; he regards Winkler's opinion, that in parthenogenetic 

 or apogamous plants there is great likelihood of a mutant keeping 

 constant, as the truest view of the question up to date, and is 

 inclined to believe that apogamy influences the constancy of a 

 mutant and causes its persistence, but is not the cause of the 

 mutation. 



* Castration and Hybridisation Experiments with some species of 

 Hieracia, by C. H. Ostenfeld. Ssertryk of Botanisk Tidsskrift. 27 Bind. 

 3, Haefte, Kobenhavn, 1906; and 



Further Studies on the Apogamy and Hybridisation of Hieracia (Experi- 

 mental and Cytological Studies on the Hieracia, by C. H. Ostenfeld and O. 

 Rosenberg. Part III.), by C. H. Ostenfeld. Sonderabdruck aus " Zeit- 

 schrift fiir induktive Abstammungs-und Vererbungslehre." Band III. 

 Heft 4. 1910. 



