OENOTHERA LAMARCKIANA 



551 



of 1 to 1. Evidently the pollen tubes of the 0. laeta grains are far 

 excelled by those of the 0. deserens pollen grains, since so many 

 more ovules are fertilized by the latter. 



Table II 

 Gamolysis of pollen of O. hybr. lucida 



The results of the tables may be summarized by saying that in 

 the hybrid 0. lucida (deserens x Lamar ckiana laeta'), the gametes 

 with a lethal factor are less effective in fertilization than those without 

 that character. The lethal ovules, as well as the lethal pollen tubes, 

 contribute a smaller part to the harvest than would be expected 

 from the ordinary rule for monohybrid splittings. In other words, 

 the 0. laeta gametes are weak in fertilization, not only as compared 

 with 0. velutina, but also in comparison with those of their own 

 type, which lack their lethal factor. From these facts it seems pro- 

 bable that the cause of this weakness is connected in some way with 

 the presence of the lethal. *) 



LITERATURE CITED. 



1. Heribert-Nilsson, N., Zuwachsgeschwindigkeit der Pollenschlauche und ge- 

 stOrte Mendelzahlen bei Oenothera Lamarckiana. Hereditas 1 : 41—67. 1920. 



2. Renner, O., Artbastarde und Bastardarten in der Gattung Oenothera. Ber. 

 Deutsch. Bot. Gesells. 35 : 21-26. 1917. 



3. Vries, Hugo de, Oenothera Lamarckiana mut. velutina. Opera VII, p. 160. 



4. , Kreuzungen von Oenothera Lam. mut. velutina. Opera VII, p. 317. 



5. , Oenothera rubrinervis, a half mutant. Opera VII, p. 353. 



(The botanical Gazette Vol. 77, 1924, p. 73). 



*) Unilaterally splitting Laefa-hybrids (Opera VII p. 326, 365, 410, 421, 

 etc.) may now be explained as splitting symmetrically, on the assumption, 

 that the empty seeds, containing Amphilaeta-germs, are for the largest part 

 suppressed by the preferential fertilization of the Velutina-gametes. 



