GENETIC CYTOLOGY IN SWEDEN 



BY 



Professor OTTO ROSENBERG 



S TO CKHOLM 



THE TENDENCY OF CYTOLOGICAL INVESTIGATION WHICH 

 aims at a connection with genetics has, in Sweden, chiefly followed two 

 lines: on the one hand, an examination of parthenogenesis, its nature and 

 causes; on the other, the study of bastard forms, in order, by an examination of 

 the chromosome conditions in the germ«cells, to obtain a clearer idea of the nature 

 of hybridizing. 



As far as the first question is concerned, Juel's important work on partheno^ 

 genesis in Antennaria alpina (1900) must be considered as being of fundamental 

 importance. His discovery that, in the embryo»sac and eggformation in the case 

 of this plant, the reduction^division is entirely absent so that, from the very be< 

 ginning, the egg has the somatic chromosome number, has later on been confirmed 

 in numerous cases; by Murbeck's investigation (1901) with respect to the poly* 

 morphic genus Alchemilla, and by examinations of Taraxacum (Juel 1905), Hier= 

 acium (Murbeck 1904; Rosenberg 1907) and of Eupatorium (Holmgren 1919). 



The apomictical or parthenogenetical development in the genus Hieracium 

 proved to be of special interest. Ostenfeld, by means of castration experiments, 

 had already shown that seedsformation without fertilization occurs in most species 

 of this genus. The present writer showed, later on, that the embryo«sac in the sub* 

 genus Archieracium was formed according to the .^nfennarja=scheme, while, in the 

 case of the sub«genus Pilosella, a vegetative cell in the neighbourhood of the sexual 

 embryo*sac grows out to an aposporous embryo=sac and displaces the sexual one. 



Already in Juel's -^nfennan'a=work, the supposition is put forward, that par« 

 thenogenesis is connected, in one way or another, with a previously existing bas* 

 tardizing process, an opinion which has, later on, been developed by Ernst into 

 an hypothesis of bastardizing as the cause of apogamy. 



Holmgren and the present writer also come to a similar conclusion, as the 

 result of a cytological investigation of apomictic Hieracium= and Eupatorium= 

 forms, where triploid chromosome numbers are specially characteristic. 



In respect to the cytological investigations of bastard forms, our interest is 

 chiefly attracted by the problem of the chromosomesconditions in the formation of 

 germ^cells or, more definitely, in regard to the heterotypic division. 



In 1904, the writer found in the genus Drosera a species^bastard which, in 

 cytological respects, presented features of no slight interest; especially, because the 

 germ*cells of the parent plants showed different chromosome^numbers the one 10 the 

 other 20. The bastard itself showed, as was to be expected, 30 chromosomes in 

 the somatic cells. But how does this chromosome arrangement agree with the 

 heterotypic division? Juel had previously shown that, in a 5yring-a=bastard during 

 metaphasis of the heterotypic division, there took place an extremely irregular chro* 

 mosomesdistribution, which results in sterile germ«cells. In the case of the above* 



