— 245 — 



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 I 

 have pointed out, that the attempt to make the pollen-grains of 

 Hieracia and of Cichoriece (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 J isolated .... 59 805 



— — (No. 46 4 ) J, isolated.... 160 318 



— (No. 46 4 ) £, castrated... 68 82 



— (No.48 a ) ?, isolated.... c. 70 70 1 ) 

 H. excellens x pilosella (No. 50 4 ) J, castrated... 0 oo 



— (No. 50 8 ) ?, isolated.... 7 350 



— — (No. 50 3 )?, castrated... 15 142 1 ) 



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 w T e 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 

 (Gorrens, 1905, p. 238) that H. pilosella, incanum {= H. p., velu- 

 tinum Heer & Heg.), which N äge li had sent him from Munich 

 is quite sterile; later (I.e. p. 246) he says as follows: "H. pilosella, 

 incanum vermag sich dem hiesigen Klima nicht gut anzupassen. 



*) This figure is too small. 



