= MN 
figures, but I do not think that the barren fruits are so numerous 
in the summer. 
full barren 
Mingividial eye a 100 83 
1 — eee LOO 158 
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 ercellens-offspring 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 O. Rosenberg, is the 
most natural one, and it gives the explanation of several points in 
the letters from Mendel to Nägeli, published by C. Correns 
(1905). 
(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 Carnoy’s fluid, of 
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. 46,1) was the ratio: 300 apparently good grains 
to 54 empty. With regard to the above-mentioned hybrid, A. 
pilosella >< aurantiacum, the ratio was 100 “good” to 57 empty. 
