— 234 — 



In correlation with these facts the polymorphism and the 

 power to make hybrids are not the same in the three subgenera. 

 The most polymorphic subgenus is Archieracium, of which probably 

 most of the species are apogamic; the only two hybrids of this 

 subgenus, mentioned in literature as obtained artificially by G. 

 Mendel, have both H. umbellatum — the only non-apogamic 

 species — as father 1 ). The cytological researchs by S. Murbeck 

 (1904, pp. 291—294) and H. O. Juel (1905, pp. 10—13) have given 

 the explanation af these things. Murbeck has examined three 

 species of the head-section Aurella (sub-section Vulgata and a group 

 intermediate between Vulgata and Tomentosa) and found them 

 parthenogenetic in the sense, that the eggcell becomes an embryo; 

 Juel on the other hand has found, that the development of both 

 pollen and eggcell in R. umbellatum is quite typical, just as in an 

 ordinary plant of the Composites. These results correspond very 

 well with the results of my castration experiments. 



With regard to the cytological development in species of the 

 other two subgenera nothing is to be found in the literature, but 

 Dr. 0. Rosenberg's examinations (which he will publish in his 

 paper) agree very well with my results. Worth noticing is also, 

 that G. Mendel 2 ) points out, that H. auricula is the best species 

 for making hybrids artificially and that all the offsprings of his 

 crossings after removal of the anthers have been hybrids, while 

 from H. aurantiacum as motherplant hybrids could not be raised. 

 The subgenus Stenotheca has not before been used for any expe- 

 riments at all ; but I should think the species of this subgenus would 

 behave as the other genera of Cichoriece (Taraxacum excepted). 



It is natural, that such an easy method of examining plants 

 with regard to their power to develop fruits without fertilisation as 

 that of Raunkiær has caused, that many other botanists have 

 repeated the experiments with Taraxacum and Rieracium. As 

 to Rieracium we find a short remark by H. Zahn (1904, p. 

 170), in which he mentions, that castration experiments with R. 

 boréale Fr., ssp. obliquum Jord. have succeeded. According to E. 

 Strasburger (1904, p. 117) I. B. Overton has also repeated 

 the castration experiments with the positive result. Further 0. 

 Kirchner (1905, p. 87) says briefly, that he has castrated H. 

 aurantiacum and has examined the castrated heads cytologically 



x ) G. Gorrens (1905), pp. 234-235. 

 2 ) G. Gorrens (1905), p. 230. 



