LAMARCKIANA SEMIGIGAS. 



559 



These numbers yield an asymmetrical curve, as is shown in fig. 

 I. The explanation of the asymmetrical form of the curve depends 

 on the assumption that the chance of viability became smaller with 

 an increasing number of double chromosomes. In this recpect the 

 result of the fertilization of semigigas with pollen of velutina would 

 differ essentially from that with pollen of 0. gigas. It is interesting 

 to note, therefore, that even in the living seedlings the chances are 

 better, the fewer the number of double rods. This may be proved 

 by comparing the degree of development, attained before the fall 

 of the first year, with the numbers of such bodies. Among the 81 



Fig. I. — Numbers of chromosomes in seedlings of Oenothera (latax 

 Lamarckiana) semigigasxO. (biennis x Lamarckiana) velutina; DC, doubled 

 chromosomes; S, seedlings. 



plants, 12 remained in the stage of rosettes (one of them died before 

 the fall, being very weak); 9 made a stem, but did not reach the 

 flowering period; 13 flowered, but had barren anthers, at least in 

 the beginning; and only 47 developed throughout in a normal way. 

 If we consider these four groups as a measure of the individual 



