MISCELLANEA 203 



One particularly interesting " sex-mutant " arose from a 

 cross made by Mr. Ostenfeld between Hieracium excdlans, 

 which bears female flowers only, and Hieracium aurantiacum, 

 which is hermaphrodite. The primary hybrid of Fj^ was, like 

 H. excellans, i.e., female only. It was isolated, and 53 individuals 

 obtained in F„. These were, of course, developed apogameticallv. 

 Of these 52 were Uke the primary hybrid, but one differed in 

 several features and was hermaphrodite with copious pollen, 

 ft was sterile on isolation, and did not set any seed. Mr. Osten- 

 feld speaks of it as a sex-mutant. 



Of special interest is his discovery that two apogamous species 

 i.e., H. aurantiacutn and H. piloseUa are fertile when the latter is 

 polhnated by the pollen of the former species. Nineteen indi- 

 viduals were obtained in this experiment, of which one was an 

 indubitable hybrid. 



Amongst other interesting points shown by his work, Mr. 

 Ostenfeld foimd all forms of Hieracium umbellatum normally 

 sexual except one which is apogamous ; but he states that, 

 setting aside this species, he believes himself justified in declaring 

 that almost all the numerous species of the sub-genus Archieracium 

 are apogamous. He tells us further that he found some species 

 apogamous and capable of cross fertilisation, while others 

 were only apogamous and incapable of cross fertilisation. 



!Mr. Ostenfeld points out that Professor Bateson's view that 

 no indisputable examples of non-segregating hj'brids have been 

 found amongst plants is upheld by his experiments with 

 Hieracia, which prove that the constancy of certain hybrids 

 is due to apogamy. 



Apparently all apogamous hybrids are not constant, for in 

 Mrs. Haig Thomas' experiments with apogamous seed from an 

 extracted Fo white Nicotiana,* derived by the selfing of an 

 F^ hybrid of N. Sylvestris x A^. affitiis there were produced in 

 F3 all the shades of reds, purples, and whites with coloured 

 under-surface fomid in Fi and Fg. It would seem, therefore, 

 that apogamous plants are not necessarily constant. 



A beautifully executed coloured plate containing drawings 

 of the parents and 23 hybrid offspring F^, F,, and F3 of 

 Hieracium excellans x Hieracium aurantiacum accompanies the 

 memoir. 



A New Theory of Sex Heredity. 



In a letter to "Nature," February 2-l:th, 1910, Mr. Frederick 

 Keeble, Professor of Botany at the University of Reading, pro- 

 pounded a new theory of sex heredity based, he states, on the 



* This plant had white flowers with coloured under surface. 



