366 Menders Experiments 



2. With a single exception the hybrids in question 

 form seeds capable of germination. H. echioides $ x H. 

 aurantiacum $ may be described as fully fertile ; H. prae- 

 altum $ x H. flagellare $ as fertile ; H. praealtum $ x H. 

 aurantiacum $ and H. Auricula $ x //. pratense $ as 

 partially fertile ; H. Auricula $ x H. Pilosella $ as slightly 

 fertile, and H. Auricula $ x H. aurantiacum $ as infertile. 

 Of the two forms of the last-named hybrid, the red-flowered 

 one was completely sterile, but from the yellow-flowered 

 one a single well-formed seed was obtained. Moreover it 

 must not pass unmentioned that among the seedlings of the 

 partially fertile hybrid H. praealtum $ x H. aurantiacum $ 

 there was one plant which possessed full fertility. 



[3.] As yet the offspring produced by self- fertilisation 

 of the hybrids have not varied, but agree in their characters 

 both with each other and with the hybrid plant from which 

 they were derived. 



From H. praealtum $ x H. flagellare $ two generations 

 have flowered; from H. echioides $ x H. aurantiacum $, 

 H. praealtum $ x H. aurantiacum $, H. Auricula $ x H. 

 Pilosella $ one generation in each case has flowered. 



4. The fact must be declared that in the case of the 

 fully fertile hybrid H. echioides $ x H. aurantiacum $ the 

 pollen of the parent types was not able to prevent self- 

 fertilisation, though it was applied in great quantity to the 

 stigmas protruding through the anther-tubes when the 

 flowers opened. 



From two flower-heads treated in this way seedlings 

 were produced resembling this hybrid plant. A very 

 similar experiment, carried out this summer with the par- 

 tially fertile H. praealtum $ x H. aurantiacum $ led to the 

 conclusion that those flower-heads in which pollen of the 

 parent type or of some other species had been applied to 

 the stigmas, developed a notably larger number of seeds 

 than those which had been left to self- fertilisation alone. 

 The explanation of this result must only be sought in 

 the circumstance that as a large part of the pollen-grains 

 of the hybrid, examined microscopically, show a defective 

 structure, a number of egg-cells capable of fertilisation do 



