a) _. 
This examination gives only the minimum of the barren pollen- 
cells, as it is quite possible, that many of the apparently good 
ones would not be able to germinate. In my earlier papers | 
have pointed out, that the attempt to make the pollen-grains of 
Hieracia and of Cichorieæ (in general) germinate led to no posi- 
tive result, a fact which previously has been found both by H. 
Molisch and B. Lidforss, but which only shows, that we do 
not know the conditions proper for germination. The pollen of H. 
pilosella and H. auricula is apparently good and nearly without 
barren grains. 
(4) The fruiting-power of the hybrids is very slight, but also 
here the same heterogeneity occurs as in the other characters. 
The following figures will give some idea of this, but it is neces- 
sary to remember that the figures of the full fruits probably are 
too high as I have counted them according to their external 
appearance and only here and there opened a fruit for closer exa- 
mination; the very few plants obtained from my sowings give a 
clear proof of that fact, even if other circumstances have also to 
be considered. 
full empty 
H. excellens x aurantiacum (No. 46,) SF, isolated.... 59 805 
— = (No. 46,) $, isolated.... 160 318 
— — (No.46,) $, castrated... 68 821) 
= — (No 280, isolated. 7.017040) 
H. excellens x pilosella.... (No. 50,) Ÿ, castrated... OMKR 
= — (No:50:) © isolated. :.1 7 350 
= — (No. 50,) 9, castrated... 15 1421) 
The whole question of the reduced fruiting-power is a very 
interesting one, but we know at present very little about this. 
Several things tend to show, that the outer conditions are of great 
importance here, and perhaps we shall succeed in finding out 
these conditions, so that we may be able to increase or to diminish 
this power. Botanists have often found, that a Hieracium-species 
in certain places does not give any fruits at all. Mendel says 
(Correns, 1905, p. 238) that H. pilosella, incanum (= H. p., velu- 
tinum Heer & Heg.), which Nägeli had sent him from Munich 
is quite sterile; later (1. c. p.246) he says as follows: “H. pilosella, 
incanım vermag sich dem hiesigen Klima nicht gut anzupassen. 
1) This figure is too small. 
