— 244 — 



figures, but I do not think that the barren fruits are so numerous 



We will come back to this point again. This female species 

 gives hybrids, when crossed with H. aurantiacum and with H.pilo- 

 sella. The crossings are carried out in that way, that heads of the 

 father-plant are carefully rubbed against the heads of the mother- 

 plant, both kinds having been opened under isolation. The offspring, 

 harvested from this procedure, consist of (1) numerous plants of 

 H. excellens, like the mother in all parts, and (2) a few hybrids. 

 The pure exçellens-oûsiprmg have without doubt been developed 

 from apogamic ovules, while the hybrids may be supposed to have 

 developed from ovules, which require fertilisation, and which, in 

 the cases where heads of H. excellens are isolated or castrated, 

 would not be able to give fruits. This supposition which is sup- 

 ported by the cytological investigations of 0. Rosenberg, is the 

 most natural one, and it gives the explanation of several points in 

 the letters from Mendel to Nägeli, published by G. G or rens 



(3) The most prominent phenomenon with regard to the hy- 

 brids is, that hybrids arising from the same cross are heterogeneous, 

 just as pointed out by Mendel (1870, p. 50). As hitherto I has 

 only rather few hybrids at my disposal, my opinion may be wrong, 

 but it seems to me, that, taken as a whole, the hybrids are nearer 

 to the mother than to the father. Further the hybrids which are 

 farthest from the mother, are not so strong as the others. Curiously 

 enough most of these hybrids are purely female like the mother, 

 a few are hermaphrodite like the father, but the pollen is for the 

 most part barren. 



As the pollen-cells contain a resinous substance, it is not 

 possible to examine them before removal of this substance. I have 

 removed it by treating the pollen-cells with Garnoy's fluid, o£ 

 which the chloroform dissolves the substance in such a way that 

 I was able to examine the contents. The result of my examina- 

 tion of the pollen-cells of the hermaphrodite hybrid, H. excellens x 

 aurantiacum (No. 46, 4) was the ratio : 300 apparently good grains 

 to 54 empty. With regard to the above-mentioned hybrid, H. 

 pilosella x aurantiacum, the ratio was 100 "good" to 57 empty. 



in the summer: 



full 

 100 

 190 



1 individual 

 1 — 



(1905). 



