264 



In this hybrid there is thus full constancy with regard to the 

 second and the third generation, just as in the two first hybrids of 

 }1. exce liens x aurantiaciim. 



b. In the summer of 1904 another cross with H. exxcllens and H. au- 

 rantiacuiii was made, using another specimen of H. aurantiacuin. The 

 result was, besides some pure H. excellens, one hybrid (No. 48 a) which 

 was near to the mother in characters. It differed in having somewhat 

 larger and more dark-hairy heads and, at least, in some of the outer 

 yellow corollas, a distinct, though often small and feeble red stripe on the 

 underside. Like the mother the hybrid was purely female. It is still alive. 



By castration was obtained only one individual of F., and by 

 several isolations altogether 13 individuals, aU alike und like Fj. By 

 means of isolation a third generation, F3, consisting of 106 individuals 

 came out, all alike, still with individual differences with regard to 

 the intensity of the feeble reddish tint on the underside of the 

 marginal corollas. As in the first reported cross here also constancy 

 in the later hybrid generations rules. 



C. A cross between H. cxcellens and H. aurnntiacum, made in 1907, 

 produced one hybrid, which quite resembled the just mentioned 

 No. 48 a, but has not been studied further. 



All the experiments here reported on show that the crosses 

 between H. excellens and H. auraiitiacuni give a heterogeneous 

 Fj, but that each individual of these primary hybrids is 

 able to produce a quite constant and homogeneous off- 

 spring, if it is not quite sterile. The explanation of this constancy 

 is probably that the offspring comes from seeds developed 

 apogamically. The one mutant in F2 of No. 463 is hitherto an 

 isolated fact, which does not allow far reaching conclusions, still it 

 shows that also apogamic plants are able to mutate. 



The little table (IV) given here recapitulates the number of hybrid 

 offspring produced during the experiments: 



Table IV. 

 Number of Hybrid-Offspring of Hieraciuni excellens x H. aitrantiacum. 



